B3 is a murine monoclonal antibody (mAb) that recognizes a LewisYcarbohydrate antigen present on the surface of many carcinomas. An imaging and Phase I trial was performed to study the ability of 111In-mAb B3 to image known metastasis and determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), kinetics,and biodistribution of 90Y-mAb B3. Patients(n = 26) with advanced epithelial tumors that express the LewisY antigen were entered. All patients received 5 mCi of 111In-mAb B3 for imaging. 90Y-mAb B3 doses were escalated from 5 to 25 mCi in 5-mCi increments. 111In-mAb B3 and 90Y-mAb B3 were coadministered over a 1-h infusion. Definite tumor imaging was observed in 20 of 26 patients. Sites imaged included lung, liver, bone, and soft tissues. The MTD of 90Y-mAb B3 was determined to be 20 mCi. The DLTs were neutropenia and thrombocytopenia. Tumor doses ranged from 7.7 to 65.1 rad/mCi. 111In- and 90Y-mAb B3 serum pharmacokinetics (n = 23) were found to be similar. The amount of B3 administered (5, 10, and 50 mg) did not alter the pharmacokinetics. Bone marrow biopsies (n = 23) showed 0.0038 ± 0.0016% of injected dose/gram for 111In-mAb B3 compared to 0.0046 ± 0.0017% of injected dose/gram for 90Y-mAb B3 (P = 0.009). When given to patients with carcinomas that express the LewisY antigen, 111In-mAb B3 demonstrated good tumor localization. The MTD of 90Y-mAb B3 is 20 mCi, with myelosuppression as the DLT. Higher doses of radioactivity need to be delivered to achieve an antitumor effect. Humanized mAb B3 is being developed for evaluation in radioimmunotherapy. A clinical trial to explore the use of higher doses of 90Y-mAb B3 with autologous stem cell support is planned.

The use of radiolabeled mAbs2 for radioimmunotherapy has been evaluated extensively in hematological malignancies and in some epithelial cancers (1, 2). Whereas therapeutic responses have been observed in patients with lymphoma and leukemia (3, 4, 5, 6), results in patients with epithelial tumors have been disappointing (7, 8, 9). These poor responses are generally attributed to limitations in antibody delivery and unfavorable tumor dosimetry. Tumor dose is affected by the delivery of radiolabeled antibody, which is in turn dependent on physical barriers to antibody delivery (10, 11), antigen density, and physical characteristics of the radionuclide (12).

In this study, we determined whether mAb B3, a murine IgG1κ that reacts with the LewisY carbohydrate epitope (B3 antigen;Ref. 13), would serve as a target for radioimmunotherapy. This epitope is present on a large number of glycoproteins and is abundantly and uniformly expressed by most carcinomas, including >95% of colorectal cancer, 80% of breast cancer, and 60% of non-small cell lung cancer as well as esophageal, gastric, pancreatic, ovarian, and bladder carcinomas. In contrast, mAb B3 has limited reactivity with normal tissues. mAb B3 has been chemically linked to a truncated form of Pseudomonas exotoxin to form immunotoxin B3-LysPE38 (LMB-1). In a Phase I clinical trial, LMB-1 was given to 38 cancer patients with tumors that react with mAb B3. In that study, five objective responses(1 complete remission, 1 partial remission, and 3 minor responses) were observed (14), indicating that the B3 antigen can be used as target for cancer therapy.

To explore the usefulness of B3 antigen as a target for radioimmunotherapy, preclinical experiments were conducted. When injected into immunodeficient mice bearing a human epidermoid carcinoma that expresses the B3 antigen, 111In-B3 showed selective and progressive accumulation at the tumor site (15). These results and preclinical biodistribution studies using 88Y-mAb B3 (16, 17) indicated that radiolabeled B3 warrants further clinical evaluation.

Whereas the largest number of radioimmunotherapy studies have focused on using 131I-labeled antibodies, several limitations have been identified, including rapid dehalogenation (18, 19)and emission of high-energy γ-rays, which imposes certain radiation safety constraints. 90Y has been evaluated as an alternative to 131I for radioimmunotherapy because of its ready availability from a 90Sr/90Y generator (20) and its physical and biological characteristics (21, 22, 23, 24). Whereas 90Y has favorable characteristics for therapy [t1/2 =64 h; pure β-emission (Emax = 2.28 MeV)], the lack of γ-ray emission makes it suboptimal for imaging and assessing biodistribution (12). To trace the biodistribution of 90Y, 111In has been used as a surrogate marker because it has similar coordination chemistry (25, 26) and metabolic handling (19, 22). In this study, we carefully compared the differences in biodistribution between 111In- and 90Y-labeled B3. Prior studies using weaker chelates have shown significant differences between 111In and 90Y (23, 24). Newer chelates have greater in vitro and in vivostability (16, 27, 28). Nevertheless, even with improved chelates, some differences between 111In and 90Y have been observed (17, 24). Using a different antibody labeled with 111In and 90Y via the 1B4M chelate (also known as Mx-diethylenetriamine pentaacetic acid; Ref. 27) in patients with adult T-cell leukemia (3), we have previously shown that there are differences in biodistribution between these two radiolabels, although these differences were small (29). Other investigators have also used the same chelate conjugate to label other antibodies (30, 31, 32); nevertheless, this is the first detailed pharmacokinetic comparison of these two isotopes using this chelate in epithelial tumors.

This study presents the results of a clinical trial in patients with advanced carcinomas that express the B3 antigen. We studied the ability of 111In-1B4M-mAb B3 to image known metastasis and performed a Phase I trial to determine the toxicities,pharmacokinetics, and the MTD of 90Y-1B4M-mAb B3.

B3 mAb.

mAb B3 is a murine IgG1 developed as described previously (13). The mAb B3 used for this clinical trial was purified by Verax Co. (Lebanon, NH) from low serum culture medium using ion-exchange chromatography. It was over 95% pure as established by SDS-PAGE.

Conjugation and Labeling.

The B3 mAb was conjugated to 2-(4-isothiocyantobenzyl)-6-methyl-diethylenetriamine pentaacetic acid(1B4M-diethylenetriamine pentaacetic acid; Ref. 27). Radiolabeling was performed with pharmaceutical grade 111In(DuPont New England Nuclear, Wilmington, DE) for imaging and/or pharmaceutical grade 90Y for therapy (DuPont New England Nuclear). In brief, 1.0–1.2 mg of conjugated mAb B3 was put into a polypropylene vial that served as the reaction vessel. For 111In, 10.2–23.2 mCi were added to the reaction vessel and allowed to react for 1 h. For 90Y labeling, the starting amount of radioactivity and antibody dose depended on the dose level to be used. Typically, 8.9–53.3 mCi of 90Y were incubated with 1.08–4.31 mg of the conjugate for 15 min. After the initial eight patients’ 90Y labeling, the method was modified to add ascorbate (11 mg/0.05 ml) as a radioprotectant during the incubation with 90Y. Excess DTPA(10−4m) was then added to the incubation mixtures to form complexes with unreacted ionic isotope. The mAb B3-bound fraction was separated by preparative size-exclusion high-performance liquid chromatography (3). Purification resulted in a final product with >99% antibody-bound 111In or 90Y. The 90Y fraction was mixed with 25% HSA to yield a 2.5% HSA solution. Purity was determined by instant thin-layer chromatography using silica gel-impregnated glass fiber sheets (2:2:1, 10% ammonium formate in water/methanol/0.2 m citric acid) and paper chromatography using saline solvent and Whatmann #1 paper pretreated with 5% HSA. The final product was filtered using a sterile 0.22-μm low-protein-binding filter (Millex-GV; Millipore, Inc., Bedford, MA). The specific activities of the 111In-mAb B3 doses(n = 26) ranged from 4.3–13.0 mCi/mg (7.3 ± 1.8 mCi/mg). The total 111In activity injected ranged from 3.5–5 mCi. The specific activities of the 90Y-mAb B3 doses(n = 23) ranged from 5.3–12.9 mCi/mg (8.4 ± 1.7 mCi/mg), with individual doses of 5–25 mCi of 90Y-mAb B3. All products passed sterility and pyrogen testing. The 111In-labeled products were injected within 72 h of preparation. Twenty-two of 23 90Y-mAb B3 doses were injected the day of labeling, whereas one product was injected the next day (24 h). The dose injected the day after labeling was retested before injection and showed similar protein-bound radioactivity.

The immunoreactivity of the radiolabeled products was tested using a modification of the cell-binding assay described by Lindmo et al.(33). In brief, an increasing number of A431 cells were incubated in 6-well plates in cell numbers ranging from 4 × 105 to 1 × 106. A small fixed amount of the radiolabeled B3 was added to the wells and incubated for 2 h. After incubation, the wells were washed, and the percentage of activity bound to cells was determined. Overall, the cell binding assay for the 111In and 90Y preparations was not significantly different, with a mean ± SD of 69 ± 10%and 69 ± 17% for 111In- and 90Y-mAb B3,respectively. When the immunoreactivity from 90Y preparations labeled in the absence of ascorbic acid were compared with those labeled in the presence of ascorbic acid, a significant difference was observed (58 ± 10% and 74 ± 18%,respectively).

Patient Selection.

Adult patients with metastatic gastrointestinal tract, breast,non-small cell lung, bladder, and ovarian carcinoma who had failed standard therapy were eligible for this study. Tumors expressed B3 antigen on ≥30% of the tumor cells as determined by immunohistochemistry. Tumor histology was confirmed by a NIH pathologist. Other eligibility criteria included: (a)advanced unresectable disease; (b) failed conventional chemotherapy; (c) Eastern Cooperative Oncology Group performance status of ≤2; (d) a minimum life expectancy of 3 months; (e) serum creatinine < 1.6 mg/dl;(f) serum bilirubin < 1.5 mg/dl; (g)absolute neutrophil count (ANC) > 2,000/mm3; and(h) platelets > 100,000/mm3. Patients with clinically significant cardiac disease (New York Heart Association grade 3 or 4) were excluded, as were those with infectious disease that required antibiotic therapy, brain metastasis, prior exposure to murine antibodies, pregnancy, or lactation. Patients who had received bone marrow transplant therapy, more than 3 chemotherapy regimens,pelvic radiation, or local radiation to more than one site were excluded. The clinical protocol and the consent form were approved by the Institutional Review Board of the National Cancer Institute. Informed consent was obtained from all patients before participation in this study.

Study Design.

An outline of the protocol design and the number of patients entered in each group are shown in Table 1. In the initial portion of this study, three patients received 5 mCi of 111In-mAb B3. The objective was to determine whether there would be any gross unexpected sites of localization of the antibody or acute toxicities that would prompt us not to proceed with the therapy portion of the study. To provide potential therapeutic benefit, these initial patients were offered therapy with 5 mCi of 90Y-mAb B3, if they had tumor imaging, no HAMAs, and no toxic side effects or unexpected, undesirable tissue accumulation as compared with other 111In-labeled antibodies. In the second portion of the study, we evaluated whether the amount of antibody resulted in dose-dependent changes in biodistribution. Three groups of three patients each received 111In (5 mCi)- and 90Y-mAb B3 (5 mCi) mixed together with 5, 10, or 50 mg of unlabeled mAb B3. In the third and main part of the protocol, the MTD of 90Y was determined. Groups containing three patients each received escalating doses of 90Y-mAb B3 for therapy coinfused with 5 mCi of 111In and a total of 10 mg (based on a lack of dose-dependent changes at the higher amounts of mAb B3). The 90Y doses were escalated in 5-mCi intervals. Patients with hematological toxicity < grade 3 were eligible for retreatment with the same dose of 90Y if they had no evidence of disease progression and remained HAMA negative.

111In-mAb B3 and 90Y-mAb B3 were coadministered i.v. over a 1-h infusion in an outpatient setting.

Pharmacokinetics.

Intravascular kinetics were determined by counting 111In or 90Y radioactivity in blood and plasma aliquots obtained at the following times after the end of infusion: 5 min, 30 min, 1 h,2 h, 6 h, 1 day, and daily for up to 7 days after the end of the infusion. The % ID/ml was obtained by comparing the counts to a standard of the injected dose. The plasma and blood volumes were estimated at each time of treatment using a nomogram based on body surface area (34). Using the latter estimated volumes and the % ID/ml, the total % ID in the blood and plasma volume was calculated. Because the infusion time was short compared with the disposition half-life (t1/2), the intravascular data were treated similar to an i.v. bolus. The % ID/ml of blood or plasma was fitted to a biexponential curve to obtain both the α andβ phase t1/2 using a least-squares fit algorithm. Conventional pharmacokinetic parameters were then derived (35). The AUCs for the blood or plasma curves were calculated in two steps. First, the AUC from the end of antibody infusion (To) to 168 h was obtained by trapezoidal integration of the decay-corrected blood and plasma data, and then the terminal AUC was estimated using the terminal clearance rate to extrapolate from the activity retained at the last measured time point. Using this data, we then estimated additional pharmacokinetic parameters, including volume of distribution, clearance, and half-life (35). Serial 24-h urine collections were obtained for up to 96 h so that we could compare the urinary excretion of the two tracers. Whole body clearance of 111In was determined from the imaging data (see below).

Imaging.

Scintillation camera images were first recorded up to six times with a large field of view dual-headed gamma camera starting within ∼2 h of the end of the infusion and daily for up to 6 or 7 days. Analogue and digital images of anterior and posterior whole body as well as spot views (5–10 min/image) were obtained. For quantitative imaging, a 20%window centered over the 247 keV photopeak of 111In was obtained. A scatter correction method was utilized. The images were corrected for attenuation using a 99mTc flood source and allowing for the energy differences and the sensitivity of the gamma camera. A geometric mean image was then generated (in units ofμCi/pixel). For visual interpretation, individual anterior and posterior images were reviewed. SPECT of the chest, abdomen, and pelvis was recorded using a medium energy collimator; SPECT was typically performed 4 to 5 days after injection. The 111In SPECT images were obtained for visual assessment utilizing a 20% window centered over the 174 and 247 keV photopeak of 111In; the images were reconstructed using a Hamming filter with a high cutoff frequency of 0.75 cycle/cm. All images were interpreted by one experienced nuclear medicine physician.

Two quantitative image regions of interest were drawn over the liver,spleen, and L4 vertebral body on the geometric mean images. The integrated radioactivity in the organs (AUC) was then determined by trapezoidal integration up to the last time point imaged (typically 7 days), and the remaining AUC was determined by extrapolation using the terminal t1/2 of clearance. The whole body t1/2 was obtained by fitting the geometric mean concentration of 111In activity of the anterior and posterior whole body scans. Using the residence times obtained from the data above and the individual organ size, as determined from CT, the medical internal radiation dose method was used to calculate organ dosimetry (36). In brief, the integral of radioactivity in a given organ, blood, or tissue was divided by its weight(μCi ·h/g) and multiplied by the mean energy emitted per nuclear transition of the β particle from 90Y (1.99 g ·Rad/μCi/h), assuming an absorbed dose fraction of 1. The activity in L4 was determined from the region of interest analysis and integrated over time. This activity was normalized by the grams of bone marrow in L4 as estimated in standard man (37). The dose to the bone marrow was then estimated as described above.

Counting Methods.

Dual isotope counting of 111In and 90Y was performed on the patient samples. The 111In γ-ray peaks were counted in a gamma counter using a 100–500 keV energy setting. Because 90Y is counted with <4% efficiency in a gamma counter, Cerenkov counting in a beta counter was also utilized. Cerenkov counting was performed using an energy range of 0–200 keV(A4530D Packard, Downes Grove, IL) in a beta counter. Because Cerenkov counting is sensitive to quench and geometry, all samples were processed in a similar and reproducible manner as described previously (29), which included solubilizing the samples with SDS and bleaching them with 30% hydrogen peroxide to minimize quench. The counts in the samples were referred back to a standard of the injected dose that had been prepared in a similar fashion using the patients’plasma or blood to mimic the quench. The counts obtained in the gamma and beta counters were corrected for cross-talk and decay.

Bone Marrow Biopsies.

Twenty-five patients underwent bone marrow biopsy of the posterior iliac spine within 5–7 days after mAb injection. Thirteen biopsies were performed 6 days after therapy, eight were performed at 5 days after therapy, and four were performed at 7 days after initial therapy. The biopsy cores were weighed on an analytical balance and put in a conical tube with 10 ml of PBS for 1 h and analyzed as described previously (29). The core was broken with a jagged-edged glass rod. This was centrifuged for 10 min at 640 × g,and the supernatant was removed and counted (saline fraction). The pelleted core was broken with a jagged-edged glass rod and mixed with 0.5 ml of 10% SDS. The core was heated to 56°C for 30 min in an attempt to remove any cell-bound activity. After the sample cooled, 0.4 ml of 30% hydrogen peroxide was added as bleach, and the mixture was incubated at 56°C for 1 h to bleach the sample. Ten ml of distilled water were added, and the sample was again centrifuged for 10 min. The supernatant was separated for counting (SDS fraction). Perchloric acid (0.2 ml) was then added to the remaining bone chips,and the mixture was incubated at 56°C until the bone was dissolved(bone fraction). This sample was again treated with hydrogen peroxide as described above. After cooling, the sample was transferred to a counting vial with 10 ml of distilled water. All samples were then counted in the gamma and beta counters with the appropriate decay and cross-talk corrections.

To attempt to find parameters that predict bone marrow toxicity, we correlated the dose to bone marrow based on imaging, bone marrow biopsy, and blood retention of 90Y. The dose to the blood was calculated as described above, and the dose to the marrow was then determined by multiplying times the red marrow:blood ratio as described by Sgouros et al.(38). The dose from marrow biopsies was determined by calculating the activity concentrated in the marrow by gamma counting of a precisely weighted specimen. We assumed that there was no biological clearance from the marrow, based on gamma camera imaging. The dose was then calculated as described above, with no corrections for cortical bone. In addition, we correlated toxicity to the bone marrow with administered activity or administered activity corrected for body weight.

HAMA Assays.

HAMA assay was performed as described previously using a high-performance liquid chromatography method (39). More than 10% complex formation using a 125I isotype matched nonspecific mAb (BL-3) and 125I-labeled B3 was considered positive.

Statistics.

To compare independent data, 111In and 90Y patient data obtained from the initial dual-injection study were used. Paired t test or Wilcoxon rank signed test (when data were not normally distributed) was performed to assess the differences in biodistribution between the two radiolabels. Pearson’s correlation coefficient was used to evaluate the relationship between nominal data,and Spearman correlation coefficient was used with ordinal data.

Patient Characteristics and Clinical Observation.

Twenty-six patients were entered into this study. Their clinical characteristics are shown in Table 2. There were 12 men and 14 women (age range, 39–73 years; mean age, 58 years). Twenty patients had colorectal cancer, 2 patients had esophageal cancer, 1 patient had gastric carcinoma, 1 patient had carcinoma of the ampulla of Vater, 1 patient had breast cancer, and 1 patient had bronchioalveolar cancer. Prior therapy and sites of metastasis are shown in Table 2. Immunohistochemical staining of B3 was performed on paraffin-embedded tumor blocks from the primary surgery in all cases. Homogeneous B3 expression was found in 23 of 26 patients. In 3 of 26 cases, specimens were poorly preserved (tightly fixed). However in all three cases, sections indicated that in the better preserved areas, more than 30% of the tumor cells were clearly positive for B3 antigen.

Infusion of unlabeled and radiolabeled antibody was well tolerated,accompanied by minimal or no side effects. Nonhematological toxicities were mild and transient (grade 1 and 2), with low-grade fever observed in four patients within 24 h after dosing. Rigor and chills were reported in one patient. Grade 1 arthralgia (one patient), myalgia (two patients), and fatigue (one patient) were observed at 2–4 weeks after dosing. Patients were treated with acetaminophen or ibuprofen as needed. It is unlikely that these symptoms were related to the therapy. As expected, the DLT was myelosuppression (see below). There were no significant changes in the chemistry profiles related to the mAb treatment. The disease status remained stable for 6 weeks in four patients. There were no clinical responses to the infusion of 90Y-mAb B3.

Imaging Results.

Twenty-one of 26 patients (85%) had localization in known sites of disease. Sites of disease imaged included liver (Fig. 1), lung (Fig. 2), bone, soft tissue mass, and lymph nodes. Table 3 shows the radiographic results and 111In-mAb B3 imaging results of individual patients.

Seventeen patients had known liver metastasis as shown by CT scan. Several imaging patterns were noted in the liver. A total of nine patients had positive uptake in the liver: six had lesions with hot rims and cold centers (Fig. 2); whereas three patients had hot lesions. Eight patients were considered negative and had either no localization or lesions that appeared cold and had some filling in on delayed imaging but were never hotter than the normal liver.

Normal sites of 111In accumulation included the liver,spleen, and bone marrow (Fig. 1). Excretion into the urinary bladder and occasional mild bowel uptake were seen. Bowel activity moved over time, indicating that it represented intraluminal activity. No gall bladder uptake was visualized. Delayed images showed progressive clearance of the blood pool and persistent accumulation in the liver and bone marrow. Lesions were better visualized on SPECT scans than on planar images (Figs. 1 and 2). No gross differences in imaging were observed at the various dose levels to suggest dose-dependent changes in biodistribution.

Pharmacokinetics.

The administered mass of mAb B3 did not have a significant effect on pharmacokinetic parameters for 111In (Table 4). No significant differences in plasma pharmacokinetics were observed between 111In- and 90Y-mAb B3 (Table 5). The blood and plasma clearance was very similar for both 111In-and 90Y-mAb B3 (Fig. 3). The amount of antibody remaining in the plasma volume at the end of infusion was 80.7 ± 6.1, 86.7 ± 10.6, and 90 ± 7.6%ID for the 5, 10, and 50 mg dose of 111In-mAb B3,respectively (ANOVA, P = 0.43). At 168 h after infusion, the amount of 111In-mAb B3 remaining in the plasma volume was 12.3 ± 2.0, 11.8 ± 3.0, and 12 ±1.6% ID, for the 5, 10, and 50 mg dose, respectively (ANOVA, P = 0.96).

Antibody dose did not result in significant differences in the 0–96-h urinary excretion of 111In or 90Y. Patients receiving 5 (n = 3), 10 (n = 17), or 50 mg (n = 3) of mAb B3 showed a median urinary excretion(0–96 h) of 11.9%, 15.1%, and 12.2%, respectively (Kruskal-Wallis one-way ANOVA, P = 0.26). Similarly, the median urinary excretion of 90Y at the corresponding time and doses was 9.7%, 11.1%, and 8.3%, respectively (P = 0.06).

The amount of 90Y injected did not affect the urinary excretion (0–96 h) of 90Y. Patients receiving ∼5(n = 3), 10 (n = 3), 15(n = 3), or 20 mCi (n = 6) showed no significant differences in urinary excretion of 90Y with 8.5 ± 2.2, 11.1 ± 1.0, 18.9 ± 15.1, and 13.3 ±3.7% ID excreted in 96 h, respectively (ANOVA, P = 0.35).

The urinary excretion of 111In and 90Y in the interval collected is shown in Table 6. The urinary excretion of 90Y in the first 24 h was greater than that of 111In [3.9 ± 1.6% compared with 3.4 ± 1.3% ID, respectively (P = 0.016)]. However, at 48–96 h, the urine excretion of 90Y was less than that of 111In [8.0 ± 4.8% ID excreted compared with 12.3 ± 6.3% ID, respectively (P = 0.016)].

Hematological Toxicity.

The dose and the hematological toxicity in individual patients are shown in Table 7. Hematologic DLT for this study was defined as an ANC < 500/μl for >5 days or platelets < 25,000/μl for >5 days. At doses of 5 and 10 mCi of 90Y-mAb B3, minimal to no hematological toxicity was observed. Grade 2 and grade 3 thrombocytopenia were observed at 15 and 20 mCi of 90Y-mAb B3. One instance of DLT occurred in one patient at 20 mCi of 90Y (patient 21); as a result, a total of six patients was treated at this dose level. Dose-limiting neutropenia and thrombocytopenia occurred in two patients who received 25 mCi of 90Y (patients 25 and 26). Grade 4 neutropenia(absolute granulocyte count < 500) was observed at day 28 after dosing and lasted 5 and 18 days. One patient required hospital admission and i.v. antibiotics for fever. Both patients received granulocyte colony-stimulating factor. Grade 4 thrombocytopenia(platelets = 25,000/μl) requiring platelet transfusion was observed at 18 and 25 days after dosing, lasting 42 days in one patient and 11 days in another patient.

In an attempt to obtain parameters that would predict toxicity,correlation of various indices of administered activity or bone marrow dose was correlated to either a percentage drop in WBC, ANC, or platelets or to toxicity grade in these parameters (Table 8). With the exception of estimates of bone marrow dose from imaging, the majority of the parameters showed a good correlation with changes in peripheral blood counts. The correlation of drop in blood counts or bone marrow toxicity based on the dose (mCi) administered correlated in the same range as the other parameters that corrected the dose (mCi) based on weight. The estimates of bone marrow dose based on the blood radioactivity or the 90Y accumulation in the bone marrow biopsy were in the same range and were not better predictors of toxicity than the administered activity.

Bone Marrow.

The dose of antibody (mg) did not alter the localization of radioactivity in the bone marrow. The mean concentration of 111In in the bone marrow was not significantly different for the 5, 10, or 50 mg doses and had a mean of 0.0043, 0.00391, and 0.00554% ID/g (ANOVA, P = 0.516). Similarly, no significant difference in the concentration of 90Y was seen in the bone marrow.

The concentration of radioactivity in the bone marrow did not vary depending on the dose of 90Y administered. The mean activities of 111In in the bone marrow for the 5, 10, 15,20, and 25 mCi doses were not significantly different with a mean of 0.0039, 0.0029, 0.004, 0.0027, and 0.0044% ID/g, respectively (ANOVA, P = 0.123). Similarly the % ID/g of 90Y in the bone marrow was not affected by the administered dose (ANOVA, P = 0.56).

The concentration of 111In in the bone marrow was lower than that for 90Y in the 17 patients receiving 10 mg of antibody with escalating doses of 90Y. The concentration of 111In was 0.0034 ± 0.0015% ID/g, whereas that for 90Y was 0.0047 ± 0.0015% ID/g. The distribution of the 111In and 90Y in the compartments of the bone measured (saline, SDS, and bone) were different for 111In and 90Y (Fig. 4).

On processing of the bone marrow, only a small proportion of the activity was lost due to processing. In the case of 111In,we recovered a mean of 95 ± 15% of the nonprocessed biopsy. In contrast, because of improved efficiency of bremmstrahlung generation after processing, the 90Y apparent recovery (efficiency)was 134 ± 29% of the original activity.

Dosimetry.

The doses to liver, spleen, bone marrow, and tumor were estimated based on the 111In biodistribution. The mean dose to the liver and spleen was 19.4 ± 4.5 and 22.2 ± 8.6 rad/mCi,respectively. The maximum total dose to the liver in this study was 576 rad, and the maximum total dose to the spleen was 716 rad. The dose to the bone marrow based on the AUC of blood was 4.8 ± 1.6 rad/mCi,and the marrow dose estimated from the biopsy was 8.3 ± 3.1 rad/mCi. Many of the tumors visualized were very extensive and overlapped with other tumor or normal structures; in some cases, their size could not be determined. The doses to tumors were variable and ranged from 7.7–65.1 rad/mCi. The mean dose to tumor was 25.1 ±18.3 rad/mCi.

Tumor Response.

No tumor responses were observed in this study. Stable disease was seen in 6 of 24 patients. No patient could be retreated because all patients developed HAMA response within 5–6 weeks after dosing.

During the past decade, several tumor-specific carbohydrate antigens have been identified (40). Because of their abundant expression on the surface of many epithelial cancers and their relative tissue specificity, surface carbohydrates such as LewisY are ideal for targeted therapy. Clinical trials in cancer patients have been conducted using anti-LewisYantibodies linked to toxins (14) or chemotherapy agents (41). In this study, we examined the imaging, toxicities,and pharmacokinetics of an anti-LewisY antibody termed B3 labeled with radionuclides 111In and 90Y.

We have shown here that 111In-mAb B3 has good sensitivity for imaging metastatic epithelial carcinomas that express the LewisY antigen. Twenty-one of 26 patients had positive uptake of 111In-mAb B3, as shown by planar and SPECT imaging. Sites imaged included lung, liver, bone, soft tissue masses,and lymph nodes. The ability of 111In-mAb B3 to detect known sites of metastasis was most effective when the tumor was localized in soft tissues, in particular, the peritoneal cavity and the abdominal wall. In this location, strong, localized uptake of 111In-mAb B3 was observed in eight of eight patients. This is particularly important if the agent is to be used in the setting of occult recurrences in colorectal carcinomas, ovarian carcinomas, and other gastrointestinal malignancies. Although the accumulation of 111In in the normal liver tissue makes it difficult to develop tumor€background ratios high enough to detect the malignancy,clear positive uptake was observed in 9 of 17 patients with liver metastasis. Four different patterns were observed. In some cases, the liver metastasis presented as hot lesions, whereas others had lesions with a hot rim and cold centers. Some lesions that were considered negative had either no localization or had lesions that appeared cold;however, on delayed imaging, these lesions showed some filling in but were never hotter than the normal liver. It is possible that these represent areas of necrosis and/or poor vascularization (42, 43, 44). Failure of 111In-mAb B3 to detect all tumors in this study could be due to nonhomogeneous expression of the B3 antigen in the metastatic sites or poor vascularization. It is also possible that a number of lesions detected by radiographic imaging represent reactive lymph nodes or fibrotic tissue.

The usefulness of mAb B3 as an imaging agent would need to be further evaluated in larger clinical studies in patients with small volume disease (e.g., patients with elevated carcinoembryonic antigen or CA-125 with no radiographic evidence of disease). However,the tumor localization of B3 observed in this first trial indicates that the use of this antibody as a radiotherapeutic agent warrants further investigation.

The use of 90Y-labeled antibodies directed against lymphoma has resulted in significant objective tumor responses (3, 31, 32, 45). Response in epithelial tumors has been more difficult to attain. Several radioimmunotherapy trials using 90Y have been reported previously, although the majority are preliminary reports or reports on a smaller number of patients than seen in our trial.

90Y-mAb B3 is well tolerated at doses up to 20 mCi, with neutropenia and thrombocytopenia as the dose DLTs. The MTD is in the range observed by others (3, 46, 47). Our dose estimates based on marrow biopsy were in a range consistent with that at which bone marrow toxicity would be expected at the 25-mCi dose level. Toxicity could be correlated to various 90Y parameters including administered dose, dose/kg, dose/m2, and dosimetry based on blood or biopsy. The correlation to dose based on imaging was the poorest, perhaps due to the difficulty in assessing bone marrow concentration using imaging techniques. If the bone marrow were not dose limiting, our normal organ dosimetry in liver would suggest that significantly higher doses could be utilized, if one assumes that toxicity for external beam to the liver will be similar,because the TD50/5 for liver is 2000 rad. The dosimetry estimates to tumor suggest that we could deliver doses of up to 80 mCi. The bone marrow concentration observed, based on bone marrow biopsy, is in the range of that observed with murine anti-Tac (29). The 111In concentrations from mAb B3 and mAb anti-Tac in bone marrow were 0.00378 and 0.00293% ID/g,respectively (P = 0.243 paired t test). In addition, the concentration of 90Y in the bone marrow from 90Y-B3 and anti-Tac were 0.0047 and 0.00494% ID/g,respectively (P = 0.777, paired t test).

The blood clearance of 111In- and 90Y-mAb B3 is similar to that reported previously with 1B4M chelate and other second-generation chelates (29, 48); in contrast, chelates that are less stable for 90Y have shown less concordance in preclinical models (16) or in clinical trials (49, 50).

The tumor doses that we delivered are in the general range of those reported by others using other 90Y-labeled antibodies (49, 51). The doses to other organs are generally similar,although some antibodies may have a higher concentration in the liver and therefore result in slightly higher liver doses (51, 52). These higher liver doses may be related to the presence of circulating antigen and complex formation (51), which was not present in our system.

Halpern et al.(53) have previously shown that the distribution of each mAb is unique unto itself with regard to its response to the mass effect. Because this “carrier effect” can alter not just the serum half-time of an antibody but also the organ tumor distribution of the radionuclide, we administered increasing amounts of mAb B3 to patients. No dose-dependent differences in pharmacokinetics were observed at doses of 5–50 mg of mAb B3, nor were there differences in urine excretion that related to the dose administered. Pharmacokinetic analysis indicated that there were no significant differences in plasma clearance of 111In- and 90Y-mAb B3.

Nevertheless, significant differences in urinary excretion of 111In and 90Y were observed. These consisted of slightly faster excretion of 90Y at the early times after injection but much higher excretion at later times. This probably reflects different handling of the radiometals, with possible excretion of some 111In as catabolism occurs, which would contrast with retention of 90Y, in particular, in the bone. These findings are similar to those we have reported previously with two different 90Y-radiolabeled mAbs (29, 48). The preferential accumulation of 90Y was evident as reflected by the bone marrow biopsy, which showed a mean of 1.4 times more 90Y than 111In. Using our coarse bone marrow fractionation method, it was clear that the greatest portion of 90Y retained was in the bone fraction.

In summary, we have shown here that specific targeting of the LewisY antigen using radionuclide linked to mAb B3 is feasible. It is clear that to achieve an objective antitumor effect,higher doses of radionuclide will need to be delivered. Strategies to improve the therapeutic index include peripheral autologous stem cell rescue to overcome the myelosuppression (54, 55) and i.v. infusion of EDTA to prevent binding of free 90Y to bone (56). As in external beam radiotherapy, the use of fractionated multiple doses for delivery of 90Y should also be explored. Humanized mAb B3 is presently being produced for evaluation in radioimmunotherapy. This should overcome the problem with HAMA formation. A clinical trial to explore the use of a higher dose of 90Y-mAb B3 with autologous stem cell support is being planned at the National Cancer Institute.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

                
2

The abbreviations used are: mAb, monoclonal antibody; HSA, human serum albumin; % ID, percentage of injected dose;HAMA, human antimouse antibody; AUC, area under the curve; MTD, maximum tolerated dose; SPECT, single-photon emission computed tomography; ANC,absolute neutrophil count; CT, computed tomography; DLT, dose-limiting toxicity.

Fig. 1.

111In images of a 57-year-old female with metastatic colon cancer to the liver. Images were obtained at 96 h after administration of 5 mCi of 111In and 25 mCi of 90Y. The left panel shows an anterior planar view of the abdomen, where tumor uptake is faintly visualized. The middle and right panels are a transverse and a coronal section, respectively, from a SPECT scan through the liver. The SPECT study clearly shows several focal areas of tumor uptake(arrows).

Fig. 1.

111In images of a 57-year-old female with metastatic colon cancer to the liver. Images were obtained at 96 h after administration of 5 mCi of 111In and 25 mCi of 90Y. The left panel shows an anterior planar view of the abdomen, where tumor uptake is faintly visualized. The middle and right panels are a transverse and a coronal section, respectively, from a SPECT scan through the liver. The SPECT study clearly shows several focal areas of tumor uptake(arrows).

Close modal
Fig. 2.

Images from a 52-year-old female with metastatic colorectal cancer to the left lung. Antibody imaging was performed 120 h after i.v. administration of 5 mCi of 111In and 20 mg of mAb B3 (the patient was coinjected with 20 mCi of 90Y-mAb B3). The left panel shows a posterior planar view of the chest, showing a focal area of increased uptake in the left lung (arrow). The middle panel is a transverse SPECT through the lung lesion, and the right panel is the corresponding CT.

Fig. 2.

Images from a 52-year-old female with metastatic colorectal cancer to the left lung. Antibody imaging was performed 120 h after i.v. administration of 5 mCi of 111In and 20 mg of mAb B3 (the patient was coinjected with 20 mCi of 90Y-mAb B3). The left panel shows a posterior planar view of the chest, showing a focal area of increased uptake in the left lung (arrow). The middle panel is a transverse SPECT through the lung lesion, and the right panel is the corresponding CT.

Close modal
Fig. 3.

The % ID of 111In-mAb B3 in the plasma volume was determined (see “Materials and Methods”). 111In and 90Y intravascular retention is very similar, although small differences were seen. The data are plotted as the mean ± SD from all 23 patients undergoing paired studies.

Fig. 3.

The % ID of 111In-mAb B3 in the plasma volume was determined (see “Materials and Methods”). 111In and 90Y intravascular retention is very similar, although small differences were seen. The data are plotted as the mean ± SD from all 23 patients undergoing paired studies.

Close modal
Fig. 4.

Bone marrow concentrations of 111In and 90Y were determined. Bone marrow biopsies were processed as described in “Materials and Methods.” Radioactivity in the bone marrow from 111In-labeled mAb B3 is shown in the left columns, and radioactivity in the bone marrow from 90Y is shown in the right columns. Radioactivity is shown in the following fractions: bone fraction (▧); SDS fraction(▨); and the intravascular fraction (□). The data are expressed as the mean concentration from patients undergoing paired 111In and 90Y studies.

Fig. 4.

Bone marrow concentrations of 111In and 90Y were determined. Bone marrow biopsies were processed as described in “Materials and Methods.” Radioactivity in the bone marrow from 111In-labeled mAb B3 is shown in the left columns, and radioactivity in the bone marrow from 90Y is shown in the right columns. Radioactivity is shown in the following fractions: bone fraction (▧); SDS fraction(▨); and the intravascular fraction (□). The data are expressed as the mean concentration from patients undergoing paired 111In and 90Y studies.

Close modal
Table 1

Protocol outline

Imaging (111In-B3) (mCi)Therapy (90Y-B3) (mCi)Total B3 (mg)n
5 (optional) 
10 
50 
10 10 
15 10 
20 10 
25 10 
Imaging (111In-B3) (mCi)Therapy (90Y-B3) (mCi)Total B3 (mg)n
5 (optional) 
10 
50 
10 10 
15 10 
20 10 
25 10 
Table 2

Patient characteristics

n = 26  
Sex: 12 male, 14 female  
Age: 39–73 yrs (mean = 58)  
Tumor histology  
20 colon carcinomas  
2 esophageal cancers  
1 gastric cancer  
1 breast cancer  
1 bronchoalveolar cancer  
1 cancer of the ampulla of Vater  
Prior therapy  
Chemotherapy  
1 regimen 11 (42%) 
2 regimens 10 (38%) 
3 regimens 4 (15%) 
Hormonal 1 (3%) 
Biological (INF)a 6 (26%) 
Radiation (1 site) 3 (11%) 
No. of metastatic sites  
1 site 10 (38%) 
2–3 sites 14 (54%) 
≥4 sites 2 (7%) 
Sites of metastasis, number of patients  
Liver, 17  
Lung, 13  
Soft tissue, 8 (perit, 4; pleura, 1; abdominal wall, 3)  
Lymph nodes, 8 (chest 2, abdomen 6)  
Bone, 3  
Stomach, 2  
Effusion, 6 (pleura, 2; ascites, 4)  
n = 26  
Sex: 12 male, 14 female  
Age: 39–73 yrs (mean = 58)  
Tumor histology  
20 colon carcinomas  
2 esophageal cancers  
1 gastric cancer  
1 breast cancer  
1 bronchoalveolar cancer  
1 cancer of the ampulla of Vater  
Prior therapy  
Chemotherapy  
1 regimen 11 (42%) 
2 regimens 10 (38%) 
3 regimens 4 (15%) 
Hormonal 1 (3%) 
Biological (INF)a 6 (26%) 
Radiation (1 site) 3 (11%) 
No. of metastatic sites  
1 site 10 (38%) 
2–3 sites 14 (54%) 
≥4 sites 2 (7%) 
Sites of metastasis, number of patients  
Liver, 17  
Lung, 13  
Soft tissue, 8 (perit, 4; pleura, 1; abdominal wall, 3)  
Lymph nodes, 8 (chest 2, abdomen 6)  
Bone, 3  
Stomach, 2  
Effusion, 6 (pleura, 2; ascites, 4)  
a

INF, interferon.

Table 3

Radiographic and 111In-mAb B3 imaging results

PatientRadiographic results111In imaging results
Lung Lung+ 
 Liver Liver− (fill in only) 
  Abdomen false+ (bowel) 
Lung Lung+ 
 Liver Liver− (cold center) 
Lung Lung+ 
 Bone Bone+ 
 Mediastinum/hilar LNa Mediastinum+/ hilar+ 
Liver Liver− (cold center) 
 Periaortic LN Periaortic+ 
Pancreatic mass Pancreatic mass− 
Liver Liver+ (hot rim) 
Bone (rib) Bone+ 
 Lung (0.5 cm) Lung nodule− 
  Presaccral area false+ 
Pleura (RLL) Pleura+ 
 Liver Liver− 
 Retroperitoneal LN Retroperitoneal LN− 
 EG junction mass EG junction mass− 
Liver Liver− (fill in) 
10 Liver Liver+ (hot rim) 
 Periportal LN Periportal LN− 
 Presaccral mass Presaccral mass+ 
11 Abdominal wall Abdominal wall+ 
12 Liver Liver − (fill in) 
13 Lung Lung+ 
 Hilar LN Hilar LN− 
14 Liver Liver− (fill in) 
15 Lung Lung+ 
 Liver  
16 Lung Lung+ 
17 Liver Liver+ (hot rim) 
 Lung Lung+ 
 Retroperitoneal LN Retroperitoneal LN− 
 Ascites Ascites+ 
18 Liver Liver+ (hot rim) 
 Pelvic mass Pelvic mass + 
 Perihepatic mass Perihepatic mass+ 
 Ascites Ascites+ 
19 Abdominal wall mass Abdominal wall mass+ 
 Liver Liver− (cold lesions) 
 Lung Lung− 
 Retroperitoneal LN Retroperitoneal LN− 
 Ascites Ascites+ 
20 Stomach (linitis plastica) Stomach− 
 Ascites Ascites+ 
21 Liver Liver+ (hot rim, some cold) 
 Peritoneal mass Peritoneal mass+ 
22 Liver Liver+ (hot rim) 
 Retroperitoneal LN Retroperitoneal LN− 
23 Liver Liver+ (hot lesions) 
 Lung Lung+ 
 Pleura Pleura+ 
24 Liver Liver+ (hot lesions) 
 Bone Bone+ 
 Pleural effusion Pleural effusion− 
25 Liver Liver+ (hot rim) 
 Mesentery mass Mesenteric mass+ 
26 Lung Lung+ 
PatientRadiographic results111In imaging results
Lung Lung+ 
 Liver Liver− (fill in only) 
  Abdomen false+ (bowel) 
Lung Lung+ 
 Liver Liver− (cold center) 
Lung Lung+ 
 Bone Bone+ 
 Mediastinum/hilar LNa Mediastinum+/ hilar+ 
Liver Liver− (cold center) 
 Periaortic LN Periaortic+ 
Pancreatic mass Pancreatic mass− 
Liver Liver+ (hot rim) 
Bone (rib) Bone+ 
 Lung (0.5 cm) Lung nodule− 
  Presaccral area false+ 
Pleura (RLL) Pleura+ 
 Liver Liver− 
 Retroperitoneal LN Retroperitoneal LN− 
 EG junction mass EG junction mass− 
Liver Liver− (fill in) 
10 Liver Liver+ (hot rim) 
 Periportal LN Periportal LN− 
 Presaccral mass Presaccral mass+ 
11 Abdominal wall Abdominal wall+ 
12 Liver Liver − (fill in) 
13 Lung Lung+ 
 Hilar LN Hilar LN− 
14 Liver Liver− (fill in) 
15 Lung Lung+ 
 Liver  
16 Lung Lung+ 
17 Liver Liver+ (hot rim) 
 Lung Lung+ 
 Retroperitoneal LN Retroperitoneal LN− 
 Ascites Ascites+ 
18 Liver Liver+ (hot rim) 
 Pelvic mass Pelvic mass + 
 Perihepatic mass Perihepatic mass+ 
 Ascites Ascites+ 
19 Abdominal wall mass Abdominal wall mass+ 
 Liver Liver− (cold lesions) 
 Lung Lung− 
 Retroperitoneal LN Retroperitoneal LN− 
 Ascites Ascites+ 
20 Stomach (linitis plastica) Stomach− 
 Ascites Ascites+ 
21 Liver Liver+ (hot rim, some cold) 
 Peritoneal mass Peritoneal mass+ 
22 Liver Liver+ (hot rim) 
 Retroperitoneal LN Retroperitoneal LN− 
23 Liver Liver+ (hot lesions) 
 Lung Lung+ 
 Pleura Pleura+ 
24 Liver Liver+ (hot lesions) 
 Bone Bone+ 
 Pleural effusion Pleural effusion− 
25 Liver Liver+ (hot rim) 
 Mesentery mass Mesenteric mass+ 
26 Lung Lung+ 
a

LN, lymph node; RLL, right lower lobe;EG, esophageal-gastric.

Table 4

Pharmacokinetic parameters for 111In-mAb B3: effects of antibody mass

mAb B3 mass (mg)5 mg10 mg50 mgP
No. of patients 17  
AUC (% ID·h/ml 2.25 ± 0.76 2.18 ± 0.85 2.03 ± 0.31 0.93a 
Clearance (ml/h) 49.6 ± 18.5 54.6 ± 25.3 50.1 ± 7.8 0.88a 
t1/2 β (h) 67.2 ± 16.5 74.4 ± 46.5 75.9 ± 3.9 0.50b 
Vc (ml) 3259 ± 358 3164 ± 770 3695 ± 806 0.49a 
mAb B3 mass (mg)5 mg10 mg50 mgP
No. of patients 17  
AUC (% ID·h/ml 2.25 ± 0.76 2.18 ± 0.85 2.03 ± 0.31 0.93a 
Clearance (ml/h) 49.6 ± 18.5 54.6 ± 25.3 50.1 ± 7.8 0.88a 
t1/2 β (h) 67.2 ± 16.5 74.4 ± 46.5 75.9 ± 3.9 0.50b 
Vc (ml) 3259 ± 358 3164 ± 770 3695 ± 806 0.49a 
a

P determined by ANOVA.

b

P determined by Kruskal-Wallis test.

Table 5

Pharmacokinetic parameters based on 111In versus90Y

111In-mAb B390Y-mAb B3P
No. of patients 23 23  
AUC (% ID·h/ml) 2.23 ± 0.77 2.23 ± 0.81 0.21a 
Clearance (ml/h) 51.8 ± 22.6 51.2 ± 22.9 0.15b 
t1/2 β (h) 74.7 ± 40 77.3 ± 43 0.06b 
Vc (ml) 3215 ± 734 3227 ± 736 0.49b 
111In-mAb B390Y-mAb B3P
No. of patients 23 23  
AUC (% ID·h/ml) 2.23 ± 0.77 2.23 ± 0.81 0.21a 
Clearance (ml/h) 51.8 ± 22.6 51.2 ± 22.9 0.15b 
t1/2 β (h) 74.7 ± 40 77.3 ± 43 0.06b 
Vc (ml) 3215 ± 734 3227 ± 736 0.49b 
a

Wilcoxon signed rank test.

b

P determined by paired t test.

Table 6

Urinary excretion of 111In and 90Y after coinfusion of 111In and 90Y-mAb B3

Time (h)Paired studies
111In % ID excreted90Y % ID excretedP
0–2 0.9 ± 0.5 1.15 ± 0.65 <0.001a 
2–24 2.5 ± 1.1 2.72 ± 1.25 0.137b 
24–48 3.7 ± 2.1 2.75 ± 1.74 <0.001b 
48–72 4.3 ± 2.9 2.76 ± 2.17 <0.001a 
72–96 4.3 ± 2.2 2.51 ± 1.37 <0.001a 
0–24 3.4 ± 1.3 3.87 ± 1.63 0.016b 
24–96 12.3 ± 6.3 8.02 ± 4.82 <0.001b 
Time (h)Paired studies
111In % ID excreted90Y % ID excretedP
0–2 0.9 ± 0.5 1.15 ± 0.65 <0.001a 
2–24 2.5 ± 1.1 2.72 ± 1.25 0.137b 
24–48 3.7 ± 2.1 2.75 ± 1.74 <0.001b 
48–72 4.3 ± 2.9 2.76 ± 2.17 <0.001a 
72–96 4.3 ± 2.2 2.51 ± 1.37 <0.001a 
0–24 3.4 ± 1.3 3.87 ± 1.63 0.016b 
24–96 12.3 ± 6.3 8.02 ± 4.82 <0.001b 
a

P determined by signed rank test for nonnormally distributed data.

b

P determined by paired t test.

Table 7

Hematological toxicity

PatientDoseMyelosuppression grade
111In-B3 (mCi)90Y-B3 (mCi)B3 (mg)AGCaPlatelets
   
   
  
  
  
 
10  
10   
10   
10 50   
11 3.7 50   
12 50   
13 10 10 
14 10 10   
15 10 10   
16 15 10 
17 15 10  
18 15 10  
19 20 10  
20 20 10 
21 20 10 
22 20 10  
23 20 10  
24 4.2 20 10   
25 25 10 
26 25 10 
PatientDoseMyelosuppression grade
111In-B3 (mCi)90Y-B3 (mCi)B3 (mg)AGCaPlatelets
   
   
  
  
  
 
10  
10   
10   
10 50   
11 3.7 50   
12 50   
13 10 10 
14 10 10   
15 10 10   
16 15 10 
17 15 10  
18 15 10  
19 20 10  
20 20 10 
21 20 10 
22 20 10  
23 20 10  
24 4.2 20 10   
25 25 10 
26 25 10 
a

AGC, absolute granulocyte count.

Table 8

Correlation of toxicity with administered 90Y-mAb B3 dose and with bone marrow dose estimates

% DropToxicity grade
WBCANCPLATELETWBCANCPLATELET
mCi 0.782a 0.724 0.815 0.712 0.561 0.685 
mCi/kg 0.802 0.783 0.806 0.741 0.611 0.652 
mCi/m2 0.821 0.785 0.842 0.739 0.619 0.666 
Rad dose blood 0.753 0.728 0.737 0.635 0.569 0.558 
Rad dose bone marrow (biopsy) 0.757 0.695 0.785 0.666 0.567 0.586 
AUC (humerus) 0.353 0.0474 0.399 0.18 0.343 0.226 
AUC (L4) 0.218 0.195 0.193 0.44 0.353 0.425 
% DropToxicity grade
WBCANCPLATELETWBCANCPLATELET
mCi 0.782a 0.724 0.815 0.712 0.561 0.685 
mCi/kg 0.802 0.783 0.806 0.741 0.611 0.652 
mCi/m2 0.821 0.785 0.842 0.739 0.619 0.666 
Rad dose blood 0.753 0.728 0.737 0.635 0.569 0.558 
Rad dose bone marrow (biopsy) 0.757 0.695 0.785 0.666 0.567 0.586 
AUC (humerus) 0.353 0.0474 0.399 0.18 0.343 0.226 
AUC (L4) 0.218 0.195 0.193 0.44 0.353 0.425 
a

Pearson correlation coefficient was used for % drop data (nominal data); Spearman correlation coefficient was used for toxicity grade data (nominal data).

We thank Debby Drumm for expert technical assistance with binding assays and handling of patient samples. We also thank Nhat Le and Mark Rotman for expert technical assistance labeling the antibodies and Craig Barker for expert technical assistance with setting up the quantitative imaging.

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