Purpose: In adjuvant settings of human epidermal growth factor receptor 2 (HER2)-positive breast cancer, anthracycline-based chemotherapy followed by taxane and trastuzumab is a standard regimen. Recent studies have reported the use of anthracycline-free adjuvant chemotherapy in selected HER2-positive breast cancer patients. We conducted a single-center retrospective study to identify the characteristics of HER2-positive breast cancer patients for whom anthracyclines can be safely omitted. Methods: A total of 238 women were diagnosed with HER2-positive breast cancer and treated with neoadjuvant and/or adjuvant chemotherapy between January 1, 2008 and December 31, 2015 at Keio University Hospital. They were divided in two cohorts: an “anthracycline” cohort of 112 anthracycline-treated women and a “no anthracycline” cohort of 126 anthracycline-untreated women. Survival outcomes were estimated by Kaplan–Meier method. Results: The 3-year disease-free survival rates in the no-anthracycline and anthracycline cohorts were 91.3% and 93.1%, respectively (P = 0.692). After using a statistical method with inverse probability of treatment weighting to minimize the selection bias, no significant differences were observed between the two cohorts (adjusted hazard ratio for disease-free survival: 1.042; P = 0.909). Stratified by tumor size, no significant differences were observed between the two cohorts in the cT1N0 and cT2N0 subsets (P = 0.516 and P = 0.579, respectively). The recurrence rate was low among patients who achieved pathological complete response after receiving neoadjuvant chemotherapy with or without anthracyclines. Conclusion: Our study suggests that anthracyclines can be safely omitted in selected patients with HER2-positive breast cancer, who have cT1N0 or cT2N0 and achieved pathological complete response after receiving neoadjuvant chemotherapy.
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