Inclusion of taxanes, particularly weekly paclitaxel, in preoperative chemotherapy improves pathologic complete response rate in estrogen receptor-positive breast cancers

Background: We examined if inclusion of a taxane and more prolonged preoperative chemotherapy improves pathologic complete response (pCR) rate in estrogen receptor (ER)-positive breast cancer compared with three to four courses of 5-fluorouracil, doxorubicin, cyclophosphamide (FAC). Patients and methods: Pooled analysis of results from seven consecutive neo-adjuvant chemotherapy trials including 1079 patients was carried out. These studies were conducted at MD Anderson Cancer Center from 1974 to 2001. Four hundred and twenty-six (39.5%) patients received taxane-based neo-adjuvant therapy. pCR rates and survival times were analyzed as a function of chemotherapy regimen and ER status. Multivariate logistic and Cox regression analysis were carried out to identify variables associated with pCR and survival. Results: Patients with ER-negative cancer had higher overall pCR rate than patients with ER-positive tumors (20.1% versus 4.9%, P < 0.001). In ER-negative patients, the pCR rates were 29% and 15% with and without a taxane (P < 0.001). In ER-positive patients, the pCR rates were 8.8% and 2.0% with and without a taxane (P < 0.001). In multivariate analysis, clinical tumor size (P < 0.001), ER-negative status (P < 0.001) and inclusion of a taxane (P = 0.01) were independently associated with pCR. For patients with pCR, survival was similar regardless of ER status or the type of regimen that induced pCR. Conclusion: pCR rates increased for patients with both ER-positive and ER-negative tumors as regimens started to include a taxane and became longer. This indicates that a subset of patients with ER-positive breast cancer benefits from more aggressive chemotherapy, similarly to patients with ER-negative tumors.