Background: Although preoperative chemotherapy (PCT) was originally used to make locally advanced breast cancers (BC) operable, it is now frequently utilized to make relatively large primary tumors small enough for breast conserving treatment (BCT). A large number of studies have been performed to identify risk factors of ipsilateral breast tumor recurrence (IBTR) after breast conserving treatment for originally small tumors. However, those studies for patients (Pts) who received BCT after PCT for relatively large tumors are limited. We have done a multicenter retrospective study to identify factors which were associated with IBTR in Pts treated with BCT after PCT.

Patients and methods: From 7 Japanese hospitals, data, which regard characteristics of tumors and Pts, and treatment, of Pts who fulfilled the following criteria; 1. Female BC Pts who started PCT before January 2007 2. Her tumor was invasive, clinically solitary, and 2 cm or largerby palpation at diagnosis 3. She received 3 or more cycles of PCT 4. She received breast conserving surgery as a definitive surgery after PCT including axillary dissection or sentinel node biopsy 5. She received radiotherapy at least to the conserved breast. Pts with inflammatory BC and BC Pts who received preoperative treatment(s) other than chemotherapy were excluded. Kaplan-Meier method was used to estimate cumulative recurrence rates. Log rank test and Cox's proportional hazard model were used for statistical analyses. Receiver Operating Characteristic (ROC) Curves and C statistics were used for evaluating the prediction ability of Cox's proportional hazard model about IBTR.

Results: A total of 324 Pts were registered. The median age at diagnosis of them was 48 years old. The median size of the primary tumors by palpation at diagnosis was 4 cm. For PCT anthracycline-based regimens were used for 83 Pts, taxane-based regimens were for 29, and anthracycline-taxane regimens were for 212. One hundred forty two Pts (43.8%) received postoperative chemotherapy, 180 (55.6%) had postoperative endocrine therapy, and only 7 had postoperative trastuzumab therapy. The median follow-up period was 45 months. Nineteen Pts (5.9%) developed IBTR. The cumulative 4-year IBTR rate was 5.5%. Univariate analyses revealed that estrogen receptor (ER) status both before and after PCT, pathological nodal status after PCT, and pathologically residual invasive tumor (solitary vs. multifocal, 1.7 cm or smaller vs. 1.8 cm or larger) were statistically significantly associated with IBTR (P < 0.05 for all of them). Pathological margin status did not affect IBTR rate (P=0.73). ER status prior to PCT (positive vs. negative)(Hazard Ratio [HR], 6.76; P=0.012), size of the residual invasive tumor (1.7 cm or smaller vs. 1.8 cm or larger)(HR, 4.74; P=0.020), and pathological nodal status after PCT (0-3 positive nodes vs. 4 or more)(HR, 3.03; P=0.041) were associated with IBTR on multivariate analysis. C statistic was 78.3%.

Conclusion: Mastectomy may be a better choice for the Pts who have tumors with negative ER, pathologically large (1.8 cm or larger) residual invasive lesions after PCT, or 4 or more pathologically positive nodes after PCT in terms of local control.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-10-05.