Adjuvant taxane-based chemotherapy for early stage breast cancer: a real-world comparison of chemotherapy regimens in Ontario.

The purpose of this study was to compare survival and risk of adverse events in women with early stage breast cancer (BC) treated with (1) doxorubicin (A), cyclophosphamide (C) + paclitaxel (P), (2) fluorouracil (F), epirubicin (E), cyclophosphamide (C) + docetaxel (D), or (3) dose-dense AC-P. Retrospective cohort study including 8462 women aged ≥18 years, with resected stage I-III BC, diagnosed between 2003 and 2009 in Ontario, identified through linkage of administrative databases. Primary outcome is overall survival (OS). Secondary outcomes are emergency room (ER) visits/hospitalizations, heart failure (HF), and leukemia. 4710 women were treated with FEC-D, 2065 with AC-P, and 1687 with dd AC-P. Adjusted 5-year OS was 92.1, 87.7, and 90.3 %, for each regimen, respectively (p = 0.0006). There was no difference in OS for FEC-D and dd AC-P in the propensity score-matched analyses (HR 1.24, 95 % CI 0.99-1.55). Five-year risk of HF was also similar (HR 1.09; 0.66-1.791.4 % for dd AC-P and 1.3 % for FEC-D and, p = 0.72). Treatment with FEC-D was significantly associated with ER visits and hospital admissions (p < 0.0001). The risks of leukemia were low and similar among the 3 groups (AC-P: 0.34 %, FEC-D: 0.08 %, dd AC-P: 0.12 %; p = 0.09). Although the efficacy of the three regimens was similar to that observed in randomized trials, we report higher toxicity with the use of these regimens in clinical practice. This was especially concerning for the docetaxel-containing regimen.