Differential response from neoadjuvant chemotherapy across breast cancer subtypes.

Abstract

662 Background: Clinical trials suggest that sensitivity to chemotherapy differs across breast cancer subtypes. This study's purpose was to evaluate the clinical utility of breast cancer subtypes in the prediction of pathologic complete response (pCR) in a cohort of breast cancer patients receiving neoadjuvant chemotherapy (NACT). Methods: Patients with stage II/III breast cancer received 4 cycles of XT (capecitabine 1650 mg/m2 on days 1-14 and docetaxel 60 mg/m2 on day 8 every 3 weeks), followed by 4 cycles of FEC (fluorouracil 500 mg/m2, epirubicin 90 mg/m2, cyclophosphamide 500 mg/m2 on day 1 every 3 weeks). Immunohistochemical analysis of estrogen receptor (ER), progesterone receptor (PgR), HER2, epidermal growth factor receptor (EGFR), cytokeratin (ck) 5/6, and Ki67 was performed in core needle biopsy samples at baseline. Tumors were classified as luminal A (ER+ and/or PgR+, and Ki67 < 20%), luminal B (ER+ and PgR+, and Ki67 > 20%), HER2 (ER- PgR-, and HER2+), or triple-negative (ER-, PgR-, and HER2-). Triple-negative tumors with and without EGFR+ and/or ck 5/6+ were further classified as basal-like and non-basal-like TN (NBTN), respectively. Results: Twenty-four patients were classified as luminal A, 18 were luminal B, 10 were HER2, 12 were basal-like, and 9 were NBTN. The overall response rate was 91.8%, including a complete response in 29 patients and a partial response in 38 patients. The overall pCR rate was 15.1% (11/73). The highest pCR rate (33.3%) was observed in patients with basal-like tumors. In triple-negative patients, basal-like patients showed significantly higher pCR rate than NBTN patients (33.3% vs. 11.1%, p > 0.01). Patients with HER-2 subtype demonstrated the pCR rate of 30.0%. A higher proportion of luminal B patients had pCR than luminal A patients (16.6% vs. 4.1%, p > 0.02). With 33 months median follow-up, estimated 2-year disease-free survival for luminal A, luminal B, HER2, basal-like, and NBTN was 75.0%, 83.4%, 70%, 83.4%, and 88.9%, respectively. Conclusions: Our data indicate that breast cancer subtypes are useful predictive biomarkers of pCR in breast cancer patients treated with NACT. No significant financial relationships to disclose.