The potential value of intratumoral or s.c. injections of pegylated liposomes as locoregionally targeted therapy of tumors and their draining lymph nodes was assessed in nude mice as part of an ongoing program aimed at developing pegylated liposomal radiosensitizers for the treatment of head and neck cancers. Animals received 111In-labeled diethylenetriaminepentaacetic acid (DTPA), either encapsulated in pegylated liposomes (IDLPL) or in the unencapsulated form(111In-DTPA), as intratumoral or s.c. injections, and the local retention, locoregional nodal drainage, and systemic biodistribution were measured. After intratumoral injections, IDLPL were effectively retained in the tumor with an area under the curve(AUC) between 1 and 96 h of 2,574.4% injected dose per gram hours(%ID/g·h). The corresponding value for 111In-DTPA was 204.4%ID/g·h. Accumulation of IDLPL was seen in ipsilateral lymph nodes. The maximal ipsilateral:contralateral node ratios were 8:1 (2.2 versus 0.27%ID/g) for inguinal nodes at 24 h and 19:1 (2.5 versus 0.13%ID/g) for axillary nodes at 48 h. Unencapsulated 111In-DTPA showed no evidence of accumulation in locoregional nodes. After s.c. injection, IDLPL were cleared slowly from the injection site with an AUC between 1 and 192 h of 24,051.1%ID/g·h. Unencapsulated 111In-DTPA was cleared rapidly with an AUC between 1 and 192 h of 46.4%ID/g·h. Again, significant levels of IDLPL were detected in the ipsilateral locoregional nodes, with ipsilateral:contralateral ratios of 121:1 (57.9 versus 0.48%ID/g) at 24 h (inguinal nodes) and 17:1 (5.2 versus 0.3%ID/g) at 72 h(axillary nodes). There was no retention of unencapsulated 111In-DTPA in the draining nodes. Locoregional administration of pegylated liposomal radiosensitizers may be a useful approach for targeted therapy of head and neck tumors and their nodal metastases.

Pegylated liposomes were initially developed with the primary goal of evading rapid clearance by the reticuloendothelial system, thus allowing them to remain in the circulation for prolonged periods after i.v. injection (1). This property of pegylated liposomes has been shown to result in effective tumor targeting (2, 3, 4) and therapeutic efficacy (5) in a number of animal models. Furthermore, in clinical studies the favorable pharmacokinetics and biodistribution of pegylated liposomal doxorubicin have been shown to translate to significant activity against AIDS-related Kaposi’s sarcoma (6, 7) and against ovarian (8) and breast cancers (9).

Although the main thrust of development of pegylated liposome-encapsulated therapeutic agents has focused on systemic administration, the ability to encapsulate a range of agents stably in pegylated liposomes and the relative lack of direct toxicity after accidental local administration (10) suggests that they may also have potential applications in the sphere of locoregional drug-targeting strategies. SCCHN,2 which is characterized by a natural history of local progression and locoregional nodal spread, may serve as an ideal target for such an approach. Thus far, only limited attention has been paid to the potential worth of locoregional depot delivery of liposomal therapeutic agents. Administration of various pegylated and nonpegylated liposomal agents via the i.p. (11, 12, 13, 14, 15, 16, 17, 18), intrapleural (19), and intrathecal (20) routes has been shown to enhance local efficacy and to reduce systemic toxicity in a number of preclinical and clinical studies. By analogy, in the sphere of locoregional therapy targeted against a primary tumor and lymph node metastases, direct intratumoral and s.c. administration may be worth additional evaluation. In this article, each of these routes has been examined in detail with the aim of defining potential therapeutic roles. In particular, these data have been discussed in the context of delivery of liposome-encapsulated radiosensitizing agents.

Animal Model

Female nude mice of mixed genetic backgrounds were used in all of the experiments. The animals were bred under specific pathogen-free conditions at the Imperial Cancer Research Fund Animal Breeding Unit(South Mimms, Herts, United Kingdom). Thereafter, the animals were transferred to the Biological Services Unit at the Imperial College of Science, Technology, and Medicine, Hammersmith Hospital; housed in sterile filter-top cages on sterile bedding; and maintained on an irradiated diet and autoclaved, acidified water (pH 2.8) ad libitum.

For the studies of intratumoral injection, mice that bore human KB head and neck cancer xenograft tumors (21) were used. The xenograft tumors were established as follows. KB tumor cells were grown to confluence in vitro in 175-cm2tissue culture flasks (Falcon, Lincoln Park, NJ) in RPMI 1640 containing penicillin 100 units/ml and streptomycin 100 μg/ml,supplemented with 10% FCS (Life Technologies, Inc., Paisley, United Kingdom) at 37°C in a humidified atmosphere of 5%CO2 in air. Culture medium, 0.02% EDTA, and trypsin were supplied by the Media Production Unit at the Imperial Cancer Research Fund (Clare Hall, Herts, United Kingdom). Tumor cells were harvested by brief incubation with a 1:3 solution of trypsin/EDTA 0.02%, a single-cell suspension was prepared, and 5 ×106 tumor cells in 0.1 ml of culture medium were injected s.c. into the right flank of the mice. The animals were used for the experiment 17–21 days after tumor inoculation. For the studies of s.c. injections, non-tumor-bearing nude mice were used.

Preparation of Radiolabeled Materials

Pegylated liposome-encapsulated DTPA (Janssen Chimica, Geel,Belgium) was provided by Sequus Pharmaceuticals, Inc. (Menlo Park, CA). STEALTH liposomes are a registered trademark and have been described previously (4). Briefly, 5 ml of DTPA-containing pegylated liposomes [hydrogenated soybean phosphatidylcholine 56.2%,cholesterol 38.3%, N-(carbamoyl-methoxypolyethylene glycol 2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine sodium salt 5.3% (values expressed in % molar ratio)] were radiolabeled by incubating them with 0.5 ml of 111In-labeled oxine (Amersham International plc, Amersham, United Kingdom) containing 18.5 MBq of radioactivity. After 1 h, 4 mg of EDTA (BDH Ltd, Poole, United Kingdom) was added to chelate any residual unencapsulated 111In and to promote the prompt excretion after administration. Entrapment of 111In within the pegylated liposomes was assayed by loading a 10-μl sample on to a 20-ml Sephadex G-50 column (Pharmacia, Uppsala, Sweden). Thirty consecutive 1-ml fractions were eluted with PBS, and the activity of each fraction was counted in a Canberra Packard Minaxi 5550 gamma counter (Pangbourne, Berks, United Kingdom). Administration proceeded if the entrapment efficiency was found to be >90%.

Unencapsulated 111In-DTPA was prepared according to a method described previously (4). Briefly, a 40-μl volume of InCl3 in 0.04 m HCl containing 22.2 MBq (600 μCi) of radioactivity was titrated to pH 6.0 by the addition of 60 μl of a 3.5% solution of sodium citrate. Thereafter, 10 μl of DTPA, in 10-fold molar excess relative to the InCl3, and 100 μl of a 100 mmsolution of sodium acetate (pH 6.0) were added. The final solution was diluted with PBS to a final activity of 10 μCi/100 μl.

The choice of 111In-DTPA as the radioisotope in these studies was based on a number of factors: (a) DTPA reliably and firmly binds 111In in vitro and in vivo; (b) DTPA is a small compound with a low molecular weight, similar to that of many of the more commonly used antineoplastic cytotoxic agents; (c) 111In has a physical half-life that is sufficiently long to allow detailed analysis of biodistribution of IDLPL and unencapsulated 111In-DTPA over the 8-day period of these studies; and (d) a simple and effective means was available of radiolabeling pegylated liposomes with 111In-DTPA, which had already been validated in a previous study (4).

Administration of Radiolabeled Materials

Intratumoral Route.

Nude mice bearing KB xenograft tumors received an intratumoral injection of 5 μl of either IDLPL or unencapsulated 111In-DTPA containing 0.037 MBq (1 μCi) of radioactivity. The injection was performed using a 27-gauge butterfly needle attached via a length of fine tubing to a 100-μl Hamilton microsyringe (Anachem, Luton, Bedfordshire, United Kingdom). After delivery of the injection, the needle was withdrawn slowly from the tumor, and the entry site was observed for evidence of leakage of the injectate through the skin. In the event of observable leakage of injectate from the tumor, the animal was excluded from the study.

Groups of five mice were dissected at 1, 4, 24, 48, 72, and 96 h after intratumoral injection of either IDLPL or unencapsulated 111In-DTPA. The mice were anesthetized using inhaled isoflurane (Abbott Laboratories Ltd, Queensborough,Kent, United Kingdom) and killed by exsanguination at cardiac puncture. The aim was to evacuate the maximum blood volume obtainable(∼1.0–1.2 ml). Voided urine was also collected. Thereafter, the tumor, ipsilateral and contralateral inguinal and axillary lymph nodes,liver, spleen, kidneys, and lungs were dissected out, washed in PBS,and placed in preweighed scintillation vials (Sterilin, Stone, United Kingdom). The content of radioactivity was assessed by counting the tubes in a Canberra Packard Minaxi 5550 gamma counter. Standards of the injected material were made in triplicate and used to correct for physical decay of the 111In.

s.c. Route.

Non-tumor-bearing nude mice received a s.c. injection of 100 μl of either IDLPL or unencapsulated 111In-DTPA containing 0.37 MBq (10 μCi) of radioactivity in the right flank. The aim was to deliver the injection to an area lying approximately equidistant between the fore and hind limbs. The site of the injection,as identified by the s.c. bleb with a small margin, was then marked with a permanent marker pen to facilitate its localization at the time of dissection.

Groups of five mice were dissected at 1, 4, 24, 48, 72, 96, and 192 h after s.c. injection of IDLPL and at 15 min and at 1, 4, 24,48, 72, and 96 h after injection of unencapsulated 111In-DTPA. The animals were killed by the same protocol as detailed above. Blood and urine were collected as above. The s.c. injection site, ipsilateral and contralateral inguinal and axillary lymph nodes, liver, spleen, kidneys, and lungs were dissected out, washed in PBS, and placed in preweighed scintillation vials. The content of radioactivity was assessed by counting the tubes in the gamma counter with standards of the injected material in triplicate to correct for physical decay of the 111In, as described above.

i.v. Route.

Nude mice bearing KB xenograft tumors received an i.v. injection of 100μl of either IDLPL or unencapsulated 111In-DTPA containing 0.37 MBq of radioactivity via a lateral tail vein. Groups of five mice were dissected at 1, 4, 24, 48, 72, 96, and 192 h after i.v. injection of IDLPL and at 15 min and 1, 4, 24, 48, 72, and 96 h after the injection of unencapsulated 111In-DTPA. The mice were killed by the method described above also. Blood and urine were collected as above. The tumor, ipsilateral and contralateral lymph nodes, liver, spleen,kidneys, and lungs were dissected out, washed in PBS, and placed in preweighed scintillation vials, and the content of radioactivity was determined as above.

Intratumoral Route.

The detailed results for the biodistribution of IDLPL and 111In-DTPA after intratumoral injection are presented in Tables 1 and 2, respectively. Fig. 1 illustrates the intratumoral levels of radioactivity for both IDLPL and 111In-DTPA over the period of study. The tumor levels demonstrated prolonged retention of IDLPL over a period of up to 96 h from a maximum level of 76.4 ± 22.7%ID/g at 1 h to 15.0 ± 5.5%ID/g at 96 h. These levels compare with the corresponding values for 111In-DTPA of 66.3 ± 12.2%ID/g at 1 h and 0.36 ± 0.15%ID/g at 96 h. The AUC for IDLPL and 111In-DTPA was 2574.4 and 204.4%ID/g·h between 1 and 96 h, respectively. These data represent a 12.6-fold increase in the AUC for the liposome-encapsulated radiolabel in the tumor during the time period of the study. The different rates of clearance of the liposome-encapsulated and -unencapsulated activity are reflected by the levels of radioactivity measured in the blood. At 1 h the level of IDLPL was 0.066 ± 0.013%ID/g, which increased to a peak level of 0.59 ± 0.42%ID/g at 4 h. Low levels of circulating activity were detectable in the blood until 96 h. The peak measured value in the blood after intratumoral injection of unencapsulated 111In-DTPA was seen at 1 h at a level of 0.22 ± 0.02%ID/g. No activity was detectable in the blood at ≥48 h. The rapidity of clearance of the unencapsulated radiolabel from the tumor is clearly seen from the profile of urinary excretion of radioactivity with 45.7 ± 27.5 and 92.4 ± 62.4%ID/g present at 1 and 4 h, respectively.

Accumulation of IDLPL was also seen in the local inguinal and axillary lymph nodes over a prolonged period (Fig. 2,a). Peak levels were achieved in both the inguinal and axillary nodes at 4 h after the injection. The data confirmed that there was significant drainage and retention of liposomes within the ipsilateral compared with the contralateral lymph nodes. These values showed considerable variability, but, when analyzed according to the ratio of levels in the ipsilateral and contralateral nodal areas, there appeared to be a pattern demonstrating a progressive increase in the ratio in the ipsilateral nodes to a maximum of approximately 8:1 (2.2 versus 0.27%ID/g) for the inguinal region at 24 h and 19:1 (2.5 versus 0.13%ID/g) for the axillary nodes at 48 h. In comparison, the same data for unencapsulated 111In-DTPA showed no evidence of progressive accumulation in regional nodes, no evidence of increased uptake in the ipsilateral compared with the contralateral lymph node groups, and no suggestion of prolonged retention (Fig. 2 b).

The data for the major organs (liver, spleen, kidneys, and lungs)showed low levels of uptake of IDLPL over a prolonged period. There was evidence of accumulation of radioactivity in the liver, spleen, and kidneys, consistent with progressive deposition in these tissues,because the liposomes were gradually released from the tumor into the circulation. The lungs showed no evidence of progressive accumulation but, rather, conformed to the pattern seen for blood radioactivity. The levels of uptake of 111In-DTPA in the major organs were very low, with no evidence of progressive accumulation or retention.

s.c. Route.

The detailed results for the biodistribution of IDLPL and 111In-DTPA after s.c. injection are shown in Tables 3 and 4, respectively. Figure 3 illustrates the s.c. levels of radioactivity for both IDLPL and 111In-DTPA over the period of study. These data clearly demonstrate that the IDLPL was cleared very slowly from the injection site with 74.7 ± 9.5%ID/g retained at 192 h. These data contrast directly with those for unencapsulated 111In-DTPA, which was cleared rapidly from the s.c. injection site from a maximal level of 59.1 ± 13.7%ID/g at 15 min to 3.7 ± 1.0%ID/g at 1 h. The corresponding AUC between 1 and 192 h for IDLPL and 111In-DTPA were 24,051.1 and 46.4%ID/g·h,respectively. These data represent a 518-fold increase in the AUC for the liposome-encapsulated radiolabel at the s.c. injection site in this time period. The levels of radioactivity measured in the blood showed evidence of these different patterns of absorption. The peak blood level of IDLPL of 0.74 ± 0.09%ID/g was reached at 24 h,whereas for the unencapsulated 111In-DTPA, the maximum level of 3.2 ± 0.3%ID/g was measured in the blood at 15 min, falling rapidly to 0.27 ± 0.04%ID/g at 1 h.

Significant levels of IDLPL were detected in the ipsilateral inguinal and axillary lymph nodes for prolonged periods after s.c. injection(Fig. 4). When compared with the corresponding contralateral nodal groups, maximal ratios of 121:1 (57.9 versus 0.48%ID/g) at 24 h for the inguinal nodes and 17:1 (5.2 versus 0.30%ID/g) at 72 h for the axillary nodes were documented. These data contrast with those recorded for unencapsulated 111In-DTPA in which no significant retention of radioactivity was seen in the draining nodes, with a maximum level seen for all of the groups at 15 min. The ratios of uptake in the ipsilateral relative to the contralateral inguinal and axillary nodes were maximal at 15 min at 3.8:1 and 1.3:1, respectively. By 1 h there was no significant difference between the levels in the ipsilateral and contralateral nodes. These data would be consistent with a phase of rapid absorption from the s.c. injection site, both by means of uptake into the blood and by lymphatics, followed by prompt excretion.

The data for the major organs again revealed evidence of progressive accumulation of the IDLPL in the liver, spleen, and kidneys (but not lungs) in which maximal levels were reached at 24–48 h. This pattern was not seen with the unencapsulated 111In-DTPA,which was cleared rapidly from all of the tissues, with maximal levels measured at 15 min.

i.v. Route.

The results for the levels of IDLPL and 111In-DTPA in tumor, inguinal, and axillary nodes after i.v. injection are shown in Tables 5 and 6,respectively. For IDLPL, it can be seen that the levels of radioactivity in the tumor were significantly lower than those seen after intratumoral injection. As regards the various nodal areas, the levels were essentially uniform, with a phase of accumulation in the nodes between 1 and 24 h, relatively stable levels between 24 and 72 h, and then a gradual decline to 192 h. There was no evidence of differences between ipsilateral and contralateral groups(relative to the side of the xenograft tumor), in contrast to the findings for both the intratumoral and the s.c. injections. For unencapsulated 111In-DTPA, there was no evidence of accumulation of this radiolabel in any of the nodes, with levels essentially undetectable at 24 h and beyond.

Direct locoregional drug administration has an obvious appeal in the treatment of cancer in that it immediately achieves a high drug concentration at the desired site of action and avoids the need for initial systemic administration with all of the associated adverse effects. Intratumoral injection represents the most direct form of such treatment but, as yet, has failed to establish a role in the standard treatment of any solid cancer. This apparent paradox can be explained as being largely attributable to the following factors: (a)rapid drug clearance from the tumor interstitium; (b)dose-limiting direct normal-tissue toxicity arising from local drug diffusion; (c) normal-tissue toxicity caused by systemic absorption; and (d) efficacy of surgical excision or irradiation for lesions that are accessible to intratumoral injection. Attempts have been made to overcome the first three problems. Reduced clearance from the site of injection and attenuated local normal tissue toxicity can be achieved by immobilizing the drug in a form that binds to a local receptor (22, 23, 24) or by preparing it in a sustained-release macromolecular form that is too large to diffuse away rapidly (25, 26). The data presented here have demonstrated that pegylated liposomes can keep the entrapped agent at the tumor site with a 12.6-fold increase in the AUC within the tumor for IDLPL relative to 111In-DTPA. Inspection of Fig. 1 shows that, had dissection time points been performed beyond 96 h, the calculated difference between the AUC for encapsulated and unencapsulated 111In-DTPA would have been considerably higher. In the context of targeted delivery of radiosensitizers, the prolonged retention of IDLPL that is documented here suggests that they may act as an effective means of achieving sustained intratumor release of entrapped agents. As regards the issue of local normal tissue toxicity, Madhavan and Northfelt (10) have reported that encapsulation of doxorubicin within pegylated liposomes abrogates the severe local toxicity of this agent after inadvertent extravasation (27, 28). It is likely that encapsulation of other radiosensitizing agents, such as cisplatin or 5-iodo-2′-deoxyuridine, would afford similar protection against local toxicity. In addition, the systemic toxicity arising from the absorption of pegylated liposomal agents might reasonably be expected to be reduced, in line with the data for i.v. administration (6, 7, 8, 9). Therefore, on this basis, pegylated liposomes seem to be an attractive vehicle for the delivery of locoregional therapy.

The above considerations will only have clinical utility, however, if the contents of locally administered pegylated liposomes are released within the interstitium of the tumor. In this regard, there is compelling evidence confirming such release in tumor tissue after i.v. administration. In particular, microfluorimetric techniques have shown release of doxorubicin within xenograft tumor deposits after the initial accumulation of liposomes in the perivascular space (29, 30). Furthermore, the responses of a variety of xenograft tumors to therapeutic nonpegylated and pegylated liposomes provides a wealth of indirect evidence of the ability of the agents retained in them to become bioavailable and exert a biological effect (5). The superiority of both pegylated liposomal doxorubicin and cisplatin over the respective unencapsulated agents in this tumor model also has been confirmed in studies in which the agent was delivered by i.v. injection (31). As yet, there have been no studies of direct intratumor injection of liposomal therapeutic agents. Konno et al.(32) reported a significant reduction in the growth rate of s.c. AH-66 hepatoma tumors with little toxicity after peritumoral s.c. injections of interleukin-2 encapsulated in nonpegylated, small unilamellar vesicles.

The data from these studies of intratumoral administration suggest that this approach also may represent an effective means of targeting the locoregional lymph node drainage areas, because substances injected directly into tumor deposits may be cleared from the tumor, at least in part, via lymphatic channels in a pattern that may recapitulate the likely spread of lymphatic metastases. The validity of this approach has been supported in recent years by studies seeking to identify“sentinel nodes” in patients with breast cancer and malignant melanoma by intratumoral injections of radiolabeled colloids (33, 34). Therefore, in addition to local therapeutic effects in the tumor, direct intratumoral injection of pegylated liposomal agents may achieve the additional benefit of concentrating them within the sites of lymphatic spread over a prolonged period, without causing unacceptable local toxicity. Although the absolute levels of radiolabeled liposomes that accumulated in the locoregional nodes after intratumoral injection were relatively low, the pattern of preferential deposition in ipsilateral as opposed to contralateral nodes confirmed that there was locoregional trafficking of pegylated liposomes within the lymphatic system. The retention of the radioactivity within the nodal tissue confirmed that it remained encapsulated within a liposome;otherwise, it would have been cleared as rapidly as unencapsulated 111In-DTPA, which showed no evidence of prolonged nodal deposition. However, the relatively poorly developed lymphatic drainage of the tumors (as shown by the relatively slow clearance of 111In-DTPA after intratumoral but not s.c. injection) and the absence of lymph node metastases from KB xenograft tumors (data not shown) suggest that this model may not accurately reflect clinical situations. For SCCHN, the patterns of lymphatic metastasis occur in a predictable fashion based on tumor site, stage,and grade (35) and can be described in terms of the Memorial Sloan-Kettering Cancer Center classification (36). Furthermore, the ability to define sentinel nodes in the head and neck after intratumoral injection has been confirmed,although that particular study (33) involved patients with malignant melanoma. Therefore, it is reasonable to hypothesize that the clinical targeting of lymph nodes after intratumoral injection of pegylated liposomal radiosensitizers may be more successful in patients by virtue of the effective drainage pathways.

The s.c. space has not been evaluated in detail as a potential route of clinical administration for cytotoxic therapies, although it is used for the delivery of cytokines (IFN, interleukin 2; Ref. 37), luteinizing-hormone-releasing hormone analogues (38), and a range of agents in the palliative care setting (39). A number of preclinical studies of s.c. administered nonpegylated liposomal agents as depot preparations have been reported in the context of inflammatory/infective (40, 41, 42) and neoplastic (43, 44) disorders. Because the s.c. space itself is not a meaningful target for anticancer therapies, the use of s.c. injected pegylated liposomes is likely to be valuable only in the context of locoregionally targeted therapeutic strategies. The s.c. tissues are permeated by a rich network of lymphatic channels that drain to locoregional lymph nodes. These nodes also receive afferent lymphatic channels from primary tumor masses. Therefore, the administration of pegylated liposomal agents by the s.c. route may provide a useful means of delivering high concentrations of drugs to lymph nodes clinically involved with metastatic disease or, indeed, clinically uninvolved lymph nodes that may harbor micrometastatic disease. Kaledin et al.(45) demonstrated the ability of s.c. injections of liposomal cisplatin and hydrocortisone to reduce the incidence of regional (popliteal) lymphadenopathy after injection of murine hepatoma and pulmonary adenocarcinomas into the footpad of mice. Significantly,there was no effect on the incidence of distant metastatic disease,suggesting that the liposomal therapy was exerting only a locoregional effect. Effective lymphatic targeting of 99mTc-labeled nonpegylated liposomes administered s.c. or intralymphatically has been demonstrated in animal and clinical studies (46, 47). Allen et al.(48) have also reported the ability of 125I-radiolabeled pegylated liposomes to target the cervical and axillary nodes after s.c. injection in a rodent model. Interestingly, with their formulation of pegylated liposomes of 80- to 90-nm diameter, up to 30% of the injected radiolabel was detected in the blood between 12 and 24 h after s.c. injection. Such levels are greatly in excess of the levels reported here, which suggests that this formulation possesses a greater ability to act as a locoregional depot agent.

The studies reported here provided clear evidence of drainage of pegylated liposomes to locoregional lymph nodes. The levels achieved in the ipsilateral inguinal lymph nodes were significantly higher after s.c. injection compared with i.v. injection. That the measured radioactivity within the lymph nodes was likely to be retained within liposomes was strongly suggested by the fact that there was no evidence of the retention of unencapsulated 111In-DTPA within the locoregional lymph nodes. Therefore, it is likely that in the setting of lymph nodes involved with metastatic disease, the tumor deposits would be exposed to relatively high concentrations of the encapsulated drug. In the context of the treatment of SCCHN, this approach may be useful as a means of targeting radiation sensitizers to lymph nodes containing clinically apparent deposits of metastatic disease or even nodal areas suspected of harboring micrometastatic disease. The patterns of lymphatic drainage of the skin in the head and neck are well documented. Thus, it may be possible to inject pegylated liposomes containing radiosensitizers s.c. in an area that will drain to lymph nodes that will be included in the radiation treatment portals. If the site of the s.c. injection lies beyond the field boundaries of the radiation portal, this area will not be sensitized to the effect of the radiation, and there should be little or no additional toxicity from this strategy. However, it must be borne in mind that the s.c. space of a loose-skinned animal such as a mouse is very different from that of humans. The capacity of the s.c. space in mice is large, such that it will accommodate relatively large volumes of injectate. In contrast, the s.c. space in humans is a potential space with limited capacity, especially in areas such as the head and neck. Attempts to deliver large injection volumes in these sites is likely to be limited by pain. Nonetheless, small-volume, single or repeated injections should be feasible without excessive toxicity.

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: SCCHN, squamous cell cancer of the head and neck; DTPA, diethylenetriaminepentaacetic acid;IDLPL, DTPA encapsulated in pegylated liposomes; AUC, area(s) under the curve; %ID/g·h, % injected dose per gram hour(s).

Fig. 1.

Intratumoral levels of 111In-DTPA-labeled pegylated liposomes and 111In-DTPA after intratumoral injection in KB xenograft tumor-bearing mice. Data expressed as mean % injected dose per gram(±SD).

Fig. 1.

Intratumoral levels of 111In-DTPA-labeled pegylated liposomes and 111In-DTPA after intratumoral injection in KB xenograft tumor-bearing mice. Data expressed as mean % injected dose per gram(±SD).

Close modal
Fig. 2.

Distribution of (a) 111In-DTPA-labeled pegylated liposomes and(b) 111In-DTPA to ipsilateral and contralateral locoregional nodes after intratumoral injection. Data expressed as mean % injected dose per gram (±SD).

Fig. 2.

Distribution of (a) 111In-DTPA-labeled pegylated liposomes and(b) 111In-DTPA to ipsilateral and contralateral locoregional nodes after intratumoral injection. Data expressed as mean % injected dose per gram (±SD).

Close modal
Fig. 3.

s.c. site levels of 111In-DTPA-labeled pegylated liposomes and 111In-DTPA after s.c. injection in nude mice. Data expressed as mean % injected dose per gram (±SD).

Fig. 3.

s.c. site levels of 111In-DTPA-labeled pegylated liposomes and 111In-DTPA after s.c. injection in nude mice. Data expressed as mean % injected dose per gram (±SD).

Close modal
Fig. 4.

Distribution of (a) 111In-DTPA-labeled pegylated liposomes and(b) 111In-DTPA to ipsilateral and contralateral locoregional nodes after s.c. injection. Data expressed as mean % injected dose per gram (±SD).

Fig. 4.

Distribution of (a) 111In-DTPA-labeled pegylated liposomes and(b) 111In-DTPA to ipsilateral and contralateral locoregional nodes after s.c. injection. Data expressed as mean % injected dose per gram (±SD).

Close modal
Table 1

Biodistribution of 111In-DTPA pegylated liposomes in nude mice after intratumoral injection

Groups of five animals were dissected at 1, 4, 24, 48, 72, and 96 h after intratumoral injection of 0.037 MBq of radiolabeled liposomes,and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue1 h4 h24 h48 h72 h96 h
Urine 4.5 ± 4.2 9.4 ± 8.9 2.1 ± 0.8 3.4 ± 2.1 0.90 ± 0.55 0.64 ± 0.42 
Blood 0.066 ± 0.029 0.59 ± 0.95 0.27 ± 0.30 0.036 ± 0.029 0.014 ± 0.005 0.018 ± 0.008 
Tumor 76.4 ± 50.7 70.0 ± 43.1 34.7 ± 8.8 22.5 ± 10.1 12.8 ± 13.9 15.0 ± 12.3 
IILNa 1.2 ± 0.9 3.1 ± 2.7 2.2 ± 2.8 0.80 ± 0.72 3.2 ± 3.0 1.7 ± 1.0 
CILN 0.53 ± 0.54 1.0 ± 0.2 0.27 ± 0.08 0.28 ± 0.35 0.49 ± 0.31 0.63 ± 0.54 
IALN 3.2 ± 4.5 7.2 ± 5.6 3.0 ± 4.0 2.5 ± 3.7 2.5 ± 1.8 2.1 ± 0.9 
CALN 0.31 ± 0.10 0.81 ± 0.35 0.24 ± 0.02 0.13 ± 0.11 0.27 ± 0.26 0.51 ± 0.45 
Liver 0.9 ± 1.5 1.6 ± 0.9 0.75 ± 0.47 0.51 ± 0.55 1.2 ± 0.9 1.9 ± 1.5 
Spleen 0.12 ± 0.13 1.5 ± 1.0 0.51 ± 0.34 0.54 ± 0.64 1.3 ± 0.8 1.9 ± 1.7 
Kidney 0.26 ± 0.11 0.33 ± 0.21 0.34 ± 0.13 0.44 ± 0.21 0.67 ± 0.21 0.74 ± 0.32 
Lung 0.074 ± 0.034 0.36 ± 0.27 0.11 ± 0.09 0.032 ± 0.034 0.058 ± 0.022 0.078 ± 0.033 
Tissue1 h4 h24 h48 h72 h96 h
Urine 4.5 ± 4.2 9.4 ± 8.9 2.1 ± 0.8 3.4 ± 2.1 0.90 ± 0.55 0.64 ± 0.42 
Blood 0.066 ± 0.029 0.59 ± 0.95 0.27 ± 0.30 0.036 ± 0.029 0.014 ± 0.005 0.018 ± 0.008 
Tumor 76.4 ± 50.7 70.0 ± 43.1 34.7 ± 8.8 22.5 ± 10.1 12.8 ± 13.9 15.0 ± 12.3 
IILNa 1.2 ± 0.9 3.1 ± 2.7 2.2 ± 2.8 0.80 ± 0.72 3.2 ± 3.0 1.7 ± 1.0 
CILN 0.53 ± 0.54 1.0 ± 0.2 0.27 ± 0.08 0.28 ± 0.35 0.49 ± 0.31 0.63 ± 0.54 
IALN 3.2 ± 4.5 7.2 ± 5.6 3.0 ± 4.0 2.5 ± 3.7 2.5 ± 1.8 2.1 ± 0.9 
CALN 0.31 ± 0.10 0.81 ± 0.35 0.24 ± 0.02 0.13 ± 0.11 0.27 ± 0.26 0.51 ± 0.45 
Liver 0.9 ± 1.5 1.6 ± 0.9 0.75 ± 0.47 0.51 ± 0.55 1.2 ± 0.9 1.9 ± 1.5 
Spleen 0.12 ± 0.13 1.5 ± 1.0 0.51 ± 0.34 0.54 ± 0.64 1.3 ± 0.8 1.9 ± 1.7 
Kidney 0.26 ± 0.11 0.33 ± 0.21 0.34 ± 0.13 0.44 ± 0.21 0.67 ± 0.21 0.74 ± 0.32 
Lung 0.074 ± 0.034 0.36 ± 0.27 0.11 ± 0.09 0.032 ± 0.034 0.058 ± 0.022 0.078 ± 0.033 
a

IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

Table 2

Biodistribution of 111In-DTPA in nude mice after intratumoral injection

Groups of five animals were dissected at 1, 4, 24, 48, 72, and 96 h after intratumoral injection of 0.037 MBq of unencapsulated 111In-DTPA, and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue1 h4 h24 h48 h72 h96 h
Urine 45.7 ± 27.5 92.4 ± 62.4 0.87 ± 0.85 0.24 ± 0.21 0.19 ± 0.22 0.057 ± 0.036 
Blood 0.22 ± 0.05 0.07 ± 0.05 0.003 ± 0.002 0.000± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Tumor 66.3 ± 27.2 12.0 ± 9.0 1.3 ± 0.7 0.95 ± 0.31 0.27 ± 0.29 0.36 ± 0.33 
IILNa 0.32 ± 0.16 0.11 ± 0.11 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CILN 0.65 ± 0.56 0.13 ± 0.11 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
IALN 0.37 ± 0.11 0.10 ± 0.22 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CALN 0.40 ± 0.20 0.25 ± 0.22 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Liver 0.094 ± 0.033 0.054 ± 0.028 0.040 ± 0.009 0.030 ± 0.008 0.026 ± 0.009 0.021 ± 0.013 
Spleen 0.070 ± 0.017 0.028 ± 0.025 0.016 ± 0.011 0.024 ± 0.025 0.025 ± 0.029 0.023 ± 0.029 
Kidney 0.80 ± 0.20 0.47 ± 0.24 0.45 ± 0.11 0.40 ± 0.15 0.34 ± 0.16 0.17 ± 0.16 
Lung 0.18 ± 0.05 0.06 ± 0.04 0.005 ± 0.004 0.023 ± 0.002 0.009 ± 0.011 0.005 ± 0.002 
Tissue1 h4 h24 h48 h72 h96 h
Urine 45.7 ± 27.5 92.4 ± 62.4 0.87 ± 0.85 0.24 ± 0.21 0.19 ± 0.22 0.057 ± 0.036 
Blood 0.22 ± 0.05 0.07 ± 0.05 0.003 ± 0.002 0.000± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Tumor 66.3 ± 27.2 12.0 ± 9.0 1.3 ± 0.7 0.95 ± 0.31 0.27 ± 0.29 0.36 ± 0.33 
IILNa 0.32 ± 0.16 0.11 ± 0.11 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CILN 0.65 ± 0.56 0.13 ± 0.11 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
IALN 0.37 ± 0.11 0.10 ± 0.22 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CALN 0.40 ± 0.20 0.25 ± 0.22 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Liver 0.094 ± 0.033 0.054 ± 0.028 0.040 ± 0.009 0.030 ± 0.008 0.026 ± 0.009 0.021 ± 0.013 
Spleen 0.070 ± 0.017 0.028 ± 0.025 0.016 ± 0.011 0.024 ± 0.025 0.025 ± 0.029 0.023 ± 0.029 
Kidney 0.80 ± 0.20 0.47 ± 0.24 0.45 ± 0.11 0.40 ± 0.15 0.34 ± 0.16 0.17 ± 0.16 
Lung 0.18 ± 0.05 0.06 ± 0.04 0.005 ± 0.004 0.023 ± 0.002 0.009 ± 0.011 0.005 ± 0.002 
a

IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

Table 3

Biodistribution of IDLPL in nude mice after s.c. injection

Groups of five animals were dissected at 1, 4, 24, 48, 72, and 96 h after s.c. injection of 0.37 MBq of IDLPL, and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue1 h24 h48 h72 h96 h192 h
Urine 22.3 ± 14.5 9.6 ± 6.5 2.7 ± 2.2 3.6 ± 1.9 0.65 ± 0.27 0.61 ± 0.34 
Blood 0.44 ± 0.42 0.74 ± 0.20 0.15 ± 0.05 0.014 ± 0.005 0.011 ± 0.005 0.012 ± 0.002 
SC sitea 176.5 ± 47.0 201.2 ± 27.9 145.6 ± 40.1 144.5 ± 32.9 116.4 ± 34.2 74.7 ± 21.2 
IILN 32.0 ± 51.1 57.9 ± 28.7 25.4 ± 14.9 37.8 ± 15.2 28.6 ± 29.9 15.3 ± 17.0 
CILN 0.73 ± 0.42 0.48 ± 0.07 0.30 ± 0.10 0.32 ± 0.10 0.26 ± 0.14 0.27 ± 0.17 
IALN 4.6 ± 3.3 4.8 ± 2.5 4.9 ± 3.8 5.2 ± 3.2 3.0 ± 2.2 1.7 ± 0.5 
CALN 0.32 ± 0.16 0.33 ± 0.04 0.33 ± 0.12 0.30 ± 0.18 0.18 ± 0.06 0.21 ± 0.04 
Liver 0.23 ± 0.20 0.71 ± 0.22 1.2 ± 0.6 0.74 ± 0.26 0.34 ± 0.06 0.26 ± 0.12 
Spleen 0.26 ± 0.012 0.60 ± 0.18 0.64 ± 0.30 0.55 ± 0.21 0.31 ± 0.07 0.34 ± 0.17 
Kidney 0.48 ± 0.12 0.62 ± 0.16 0.42 ± 0.12 0.34 ± 0.07 0.26 ± 0.04 0.32 ± 0.10 
Lung 0.19 ± 0.12 0.18 ± 0.04 0.08 ± 0.02 0.042 ± 0.008 0.034 ± 0.011 0.038 ± 0.011 
Tissue1 h24 h48 h72 h96 h192 h
Urine 22.3 ± 14.5 9.6 ± 6.5 2.7 ± 2.2 3.6 ± 1.9 0.65 ± 0.27 0.61 ± 0.34 
Blood 0.44 ± 0.42 0.74 ± 0.20 0.15 ± 0.05 0.014 ± 0.005 0.011 ± 0.005 0.012 ± 0.002 
SC sitea 176.5 ± 47.0 201.2 ± 27.9 145.6 ± 40.1 144.5 ± 32.9 116.4 ± 34.2 74.7 ± 21.2 
IILN 32.0 ± 51.1 57.9 ± 28.7 25.4 ± 14.9 37.8 ± 15.2 28.6 ± 29.9 15.3 ± 17.0 
CILN 0.73 ± 0.42 0.48 ± 0.07 0.30 ± 0.10 0.32 ± 0.10 0.26 ± 0.14 0.27 ± 0.17 
IALN 4.6 ± 3.3 4.8 ± 2.5 4.9 ± 3.8 5.2 ± 3.2 3.0 ± 2.2 1.7 ± 0.5 
CALN 0.32 ± 0.16 0.33 ± 0.04 0.33 ± 0.12 0.30 ± 0.18 0.18 ± 0.06 0.21 ± 0.04 
Liver 0.23 ± 0.20 0.71 ± 0.22 1.2 ± 0.6 0.74 ± 0.26 0.34 ± 0.06 0.26 ± 0.12 
Spleen 0.26 ± 0.012 0.60 ± 0.18 0.64 ± 0.30 0.55 ± 0.21 0.31 ± 0.07 0.34 ± 0.17 
Kidney 0.48 ± 0.12 0.62 ± 0.16 0.42 ± 0.12 0.34 ± 0.07 0.26 ± 0.04 0.32 ± 0.10 
Lung 0.19 ± 0.12 0.18 ± 0.04 0.08 ± 0.02 0.042 ± 0.008 0.034 ± 0.011 0.038 ± 0.011 
a

SC site, s.c. injection site;IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

Table 4

Biodistribution of 111In-DTPA in nude mice after s.c. injection

Groups of five animals were dissected 15 minutes and at 1, 24, 48, 72,96 and 192 h after s.c. injection of 0.37 MBq of unencapsulated 111In-DTPA, and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue15 min1 h24 h48 h72 h96 h192 h
Urine 1595 ± 250 925 ± 426 1.9 ± 1.2 0.36 ± 0.24 1.5 ± 0.9 0.34 ± 0.19 0.14 ± 0.08 
Blood 3.2 ± 0.7 0.27 ± 0.10 0.004 ± 0.004 0.001 ± 0.000 0.001 ± 0.000 0.001 ± 0.000 0.000 ± 0.000 
SC sitea 59.1 ± 30.7 3.7 ± 2.2 1.1 ± 0.7 0.90 ± 0.36 0.68 ± 0.21 0.54 ± 0.02 0.30 ± 0.19 
IILN 9.5 ± 4.4 0.65 ± 0.52 0.14 ± 0.12 0.10 ± 0.02 0.067 ± 0.028 0.099 ± 0.011 0.065 ± 0.037 
CILN 2.5 ± 0.7 0.57 ± 0.78 0.032 ± 0.035 0.038 ± 0.002 0.022 ± 0.002 0.022 ± 0.012 0.038 ± 0.026 
IALN 3.8 ± 0.6 0.55 ± 0.36 0.10 ± 0.04 0.11 ± 0.04 0.072 ± 0.035 0.098 ± 0.038 0.10 ± 0.02 
CALN 2.9 ± 0.7 0.49 ± 0.43 0.07 ± 0.05 0.058 ± 0.017 0.039 ± 0.0.026 0.051 ± 0.020 0.046 ± 0.047 
Liver 0.97 ± 0.12 0.16 ± 0.05 0.050 ± 0.012 0.034 ± 0.012 0.030 ± 0.011 0.021 ± 0.003 0.021 ± 0.008 
Spleen 0.88 ± 0.12 0.13 ± 0.07 0.030 ± 0.008 0.025 ± 0.006 0.024 ± 0.006 0.016 ± 0.002 0.007 ± 0.002 
Kidney 10.8 ± 4.2 1.6 ± 0.4 0.65 ± 0.14 0.43 ± 0.07 0.31 ± 0.07 0.20 ± 0.04 0.083 ± 0.018 
Lung 2.38 ± 0.52 0.29 ± 0.13 0.014 ± 0.006 0.13 ± 0.26 0.011 ± 0.007 0.007 ± 0.002 0.006 ± 0.005 
Tissue15 min1 h24 h48 h72 h96 h192 h
Urine 1595 ± 250 925 ± 426 1.9 ± 1.2 0.36 ± 0.24 1.5 ± 0.9 0.34 ± 0.19 0.14 ± 0.08 
Blood 3.2 ± 0.7 0.27 ± 0.10 0.004 ± 0.004 0.001 ± 0.000 0.001 ± 0.000 0.001 ± 0.000 0.000 ± 0.000 
SC sitea 59.1 ± 30.7 3.7 ± 2.2 1.1 ± 0.7 0.90 ± 0.36 0.68 ± 0.21 0.54 ± 0.02 0.30 ± 0.19 
IILN 9.5 ± 4.4 0.65 ± 0.52 0.14 ± 0.12 0.10 ± 0.02 0.067 ± 0.028 0.099 ± 0.011 0.065 ± 0.037 
CILN 2.5 ± 0.7 0.57 ± 0.78 0.032 ± 0.035 0.038 ± 0.002 0.022 ± 0.002 0.022 ± 0.012 0.038 ± 0.026 
IALN 3.8 ± 0.6 0.55 ± 0.36 0.10 ± 0.04 0.11 ± 0.04 0.072 ± 0.035 0.098 ± 0.038 0.10 ± 0.02 
CALN 2.9 ± 0.7 0.49 ± 0.43 0.07 ± 0.05 0.058 ± 0.017 0.039 ± 0.0.026 0.051 ± 0.020 0.046 ± 0.047 
Liver 0.97 ± 0.12 0.16 ± 0.05 0.050 ± 0.012 0.034 ± 0.012 0.030 ± 0.011 0.021 ± 0.003 0.021 ± 0.008 
Spleen 0.88 ± 0.12 0.13 ± 0.07 0.030 ± 0.008 0.025 ± 0.006 0.024 ± 0.006 0.016 ± 0.002 0.007 ± 0.002 
Kidney 10.8 ± 4.2 1.6 ± 0.4 0.65 ± 0.14 0.43 ± 0.07 0.31 ± 0.07 0.20 ± 0.04 0.083 ± 0.018 
Lung 2.38 ± 0.52 0.29 ± 0.13 0.014 ± 0.006 0.13 ± 0.26 0.011 ± 0.007 0.007 ± 0.002 0.006 ± 0.005 
a

SC site, s.c. injection site;IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

Table 5

Biodistribution of IDLPL in nude mice after i.v. injection

Groups of five animals were dissected at 1, 24, 48, 72, 96 and 192 h after i.v. injection of 0.037 MBq of IDLPL, and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue1 h24 h48 h72 h96 h192 h
Urine 61.8 ± 24.6 8.4 ± 3.6 6.4 ± 3.5 4.3 ± 3.0 5.9 ± 2.4 3.4 ± 1.8 
Blood 34.6 ± 3.1 22.4 ± 2.5 6.4 ± 2.2 0.32 ± 0.12 0.03 ± 0.01 0.01 ± 0.00 
Tumor 1.4 ± 0.4 5.0 ± 2.7 5.1 ± 2.4 3.2 ± 1.5 1.8 ± 0.9 0.85 ± 0.36 
IILNa 1.3 ± 0.2 3.4 ± 1.2 2.2 ± 0.8 3.8 ± 0.6 2.4 ± 1.0 1.3 ± 0.4 
CILN 1.3 ± 0.2 3.0 ± 1.0 2.6 ± 0.5 3.6 ± 0.4 2.0 ± 0.3 1.1 ± 0.2 
IALN 1.9 ± 0.3 2.8 ± 0.6 2.9 ± 0.9 2.8 ± 0.4 2.0 ± 0.7 0.85 ± 0.42 
CALN 1.7 ± 0.5 2.7 ± 0.8 2.7 ± 0.9 2.7 ± 0.4 1.7 ± 0.4 1.0 ± 0.3 
Liver 5.4 ± 1.8 18.1 ± 3.2 16.9 ± 2.9 16.1 ± 3.4 13.5 ± 2.6 5.7 ± 2.4 
Spleen 6.4 ± 2.0 19.1 ± 2.6 15.6 ± 3.4 14.4 ± 2.9 11.6 ± 3.2 7.5 ± 2.3 
Kidney 6.5 ± 2.4 6.0 ± 2.6 5.4 ± 1.8 5.1 ± 1.7 4.0 ± 1.7 2.3 ± 0.9 
Lung 6.8 ± 3.0 2.4 ± 1.3 1.5 ± 0.8 0.73 ± 0.28 0.34 ± 0.15 0.20 ± 0.07 
Tissue1 h24 h48 h72 h96 h192 h
Urine 61.8 ± 24.6 8.4 ± 3.6 6.4 ± 3.5 4.3 ± 3.0 5.9 ± 2.4 3.4 ± 1.8 
Blood 34.6 ± 3.1 22.4 ± 2.5 6.4 ± 2.2 0.32 ± 0.12 0.03 ± 0.01 0.01 ± 0.00 
Tumor 1.4 ± 0.4 5.0 ± 2.7 5.1 ± 2.4 3.2 ± 1.5 1.8 ± 0.9 0.85 ± 0.36 
IILNa 1.3 ± 0.2 3.4 ± 1.2 2.2 ± 0.8 3.8 ± 0.6 2.4 ± 1.0 1.3 ± 0.4 
CILN 1.3 ± 0.2 3.0 ± 1.0 2.6 ± 0.5 3.6 ± 0.4 2.0 ± 0.3 1.1 ± 0.2 
IALN 1.9 ± 0.3 2.8 ± 0.6 2.9 ± 0.9 2.8 ± 0.4 2.0 ± 0.7 0.85 ± 0.42 
CALN 1.7 ± 0.5 2.7 ± 0.8 2.7 ± 0.9 2.7 ± 0.4 1.7 ± 0.4 1.0 ± 0.3 
Liver 5.4 ± 1.8 18.1 ± 3.2 16.9 ± 2.9 16.1 ± 3.4 13.5 ± 2.6 5.7 ± 2.4 
Spleen 6.4 ± 2.0 19.1 ± 2.6 15.6 ± 3.4 14.4 ± 2.9 11.6 ± 3.2 7.5 ± 2.3 
Kidney 6.5 ± 2.4 6.0 ± 2.6 5.4 ± 1.8 5.1 ± 1.7 4.0 ± 1.7 2.3 ± 0.9 
Lung 6.8 ± 3.0 2.4 ± 1.3 1.5 ± 0.8 0.73 ± 0.28 0.34 ± 0.15 0.20 ± 0.07 
a

IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

Table 6

Biodistribution of 111In-DTPA in nude mice after i.v. injection

Groups of five animals were dissected at 15 minutes and at 1, 24, 48,72, 96 and 192 h after i.v. injection of 0.37 MBq of unencapsulated 111In-DPTA, and the tissue content of radioactivity was assessed by counting samples in a gamma counter. Data are expressed as mean % injected dose per gram ± SD.

Tissue15 min1 h24 h48 h72 h96 h192 h
Urine 1426 ± 356 854 ± 263 0.25 ± 0.05 0.08 ± 0.04 0.04 ± 0.01 0.02 ± 0.01 0.006 ± 0.002 
Blood 3.4 ± 1.8 0.34 ± 0.16 0.02 ± 0.01 0.004 ± 0.000 0.002 ± 0.001 0.000 ± 0.000 0.000 ± 0.000 
Tumor 0.6 ± 0.2 0.34 ± 0.14 0.10 ± 0.04 0.04 ± 0.01 0.03 ± 0.02 0.02 ± 0.01 0.004 ± 0.002 
IILNa 1.2 ± 0.4 0.12 ± 0.04 0.006 ± 0.002 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CILN 1.3 ± 0.3 0.23 ± 0.14 0.012 ± 0.005 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
IALN 0.76 ± 0.25 0.16 ± 0.11 0.013 ± 0.008 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CALN 0.84 ± 0.31 0.20 ± 0.10 0.007 ± 0.004 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Liver 1.1 ± 0.4 0.17 ± 0.05 0.06 ± 0.02 0.06 ± 0.01 0.04 ± 0.01 0.04 ± 0.01 0.01 ± 0.01 
Spleen 0.38 ± 0.15 0.07 ± 0.03 0.09 ± 0.04 0.06 ± 0.02 0.05 ± 0.01 0.05 ± 0.02 0.03 ± 0.02 
Kidney 6.5 ± 3.6 1.5 ± 0.6 0.85 ± 0.32 0.64 ± 0.21 0.52 ± 0.19 0.35 ± 0.12 0.11 ± 0.05 
Lung 1.9 ± 0.6 0.11 ± 0.04 0.02 ± 0.01 0.02 ± 0.01 0.01 ± 0.01 0.007 ± 0.003 0.003 ± 0.002 
Tissue15 min1 h24 h48 h72 h96 h192 h
Urine 1426 ± 356 854 ± 263 0.25 ± 0.05 0.08 ± 0.04 0.04 ± 0.01 0.02 ± 0.01 0.006 ± 0.002 
Blood 3.4 ± 1.8 0.34 ± 0.16 0.02 ± 0.01 0.004 ± 0.000 0.002 ± 0.001 0.000 ± 0.000 0.000 ± 0.000 
Tumor 0.6 ± 0.2 0.34 ± 0.14 0.10 ± 0.04 0.04 ± 0.01 0.03 ± 0.02 0.02 ± 0.01 0.004 ± 0.002 
IILNa 1.2 ± 0.4 0.12 ± 0.04 0.006 ± 0.002 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CILN 1.3 ± 0.3 0.23 ± 0.14 0.012 ± 0.005 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
IALN 0.76 ± 0.25 0.16 ± 0.11 0.013 ± 0.008 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
CALN 0.84 ± 0.31 0.20 ± 0.10 0.007 ± 0.004 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 0.000 ± 0.000 
Liver 1.1 ± 0.4 0.17 ± 0.05 0.06 ± 0.02 0.06 ± 0.01 0.04 ± 0.01 0.04 ± 0.01 0.01 ± 0.01 
Spleen 0.38 ± 0.15 0.07 ± 0.03 0.09 ± 0.04 0.06 ± 0.02 0.05 ± 0.01 0.05 ± 0.02 0.03 ± 0.02 
Kidney 6.5 ± 3.6 1.5 ± 0.6 0.85 ± 0.32 0.64 ± 0.21 0.52 ± 0.19 0.35 ± 0.12 0.11 ± 0.05 
Lung 1.9 ± 0.6 0.11 ± 0.04 0.02 ± 0.01 0.02 ± 0.01 0.01 ± 0.01 0.007 ± 0.003 0.003 ± 0.002 
a

IILN, ipsilateral inguinal lymph node; IALN, ipsilateral axillary lymph node; CILN, contralateral inguinal lymph node; CALN, contralateral axillary lymph node.

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