Predictors of tumor shrinkage after anthracycline-based preoperative chemotherapy

Abstract

e11531 Background: Anthracyclines are currently included in several chemotherapy (CT) regimens for the treatment of breast cancer (BC). However, increasing evidence suggests that benefit from these agents is limited to some subgroups of patients (pts). Aim of this study was to identify potential predictors of tumor shrinkage (TS) in a retrospective series of pts receiving preoperative anthracycline-based CT for operable BC. Methods: The study population consisted of 94 pts with large (>2 cm), any N, operable BC treated with preoperative anthracycline-based CT. Association between clinico-biological factors and clinico-radiological TS (by caliper and MRI) was assessed. TS was calculated as the difference between the maximum tumor diameter at baseline and the maximum tumor diameter after preoperative CT/ the maximum tumor diameter at baseline x 100. Immunohistochemical analyses for biological variables (ER, PgR, HER2, MIB1, topoisomerase II alpha) were performed on pretreatment biopsies. Results: In univariate analysis, the following variables were associated with clinical TS: high MIB-1 [Odd ratio (OR) 2.6, p = 0.03], type of taxane (docetaxel vs paclitaxel: OR 0.3, p = 0.01) and number of cycles of CT (> 4 vs ≤ 4: OR 9.2, p < 0.0001). In multivariate analysis, number of cycles of CT was the only independent predictor of clinical TS (OR = 9.2, p = 0.05). In univariate analysis, the following variables were associated with MRI TS: high MIB-1 (OR 2.4, p = 0.06), tumor size (≥ 40 mm vs < 40 mm: OR 5.6, p 0 0.01), taxane CT (yes vs no: OR 4.3, p = 0.02) and number of cycles of CT (> 4 vs ≤ 4: OR 4.4, p = 0.002). In multivariate analysis, high MIB-1 was the only independent predictor of MRI TS (OR = 3.7, p = 0.03). Conclusions: High MIB-1 expression and number of cycles of chemotherapy significantly predicted tumor shrinkage in patients treated with preoperative anthracycline-based chemotherapy. Further studies are warranted to better identify patients who derive benefit from anthracyclines. No significant financial relationships to disclose.