Impact of sequence order of anthracyclines and taxanes in neoadjuvant chemotherapy on pathologic complete response rate in HER2-negative breast cancer patients

Purpose Data exploring optimal sequencing of anthracyclines and taxanes as neoadjuvant chemotherapy (NACT) for breast cancer are limited and inconsistent. The objective of this study was to assess the real-world impact of sequence order on pathologic complete response (pCR) and clinical outcomes from NACT. Methods Patients with HER2-negative breast cancer treated with NACT from May 2012 to April 2020 were identified from a prospectively collected institutional database. The primary endpoint was to compare rates of pCR (ypT0/isN0) between patients who received anthracyclines followed by taxanes (AC-T) to those who received taxanes followed by anthracyclines (T-AC). Additional endpoints of interest included clinical complete response, downstaging, Neo-Bioscore, conversion to breast-conserving surgery eligibility, relapse-free survival, and overall survival between groups. Results Of the 283 patients who met eligibility criteria, 187 (66%) received AC-T and 96 (34%) received T-AC. Sequence order did not influence the primary endpoint of pCR rate (19% for AC-T vs. 21% for T-AC, p = 0.752). There were also no significant differences in secondary NACT efficacy outcomes between groups. In the overall cohort, pCR rate was higher in patients with triple-negative breast cancer (TNBC) (32% vs. 13% in hormone-positive cancer, p