De-escalated Therapy Omitting Anthracyclines for Stage I HER2-positive Breast Cancer: A Retrospective Observational Study

Background: It is unclear whether the de-escalated therapy that omits anthracycline-based chemotherapy is as beneficial as standard therapy for patients with stage I human epidermal growth factor receptor 2-positive (HER2(+)) early breast cancer. Patients and Methods: We retrospectively investigated 95 patients with pathological stage I HER2(+) early breast cancer who underwent adjuvant treatment from April 2009 to December 2018. Results: We assessed 45 patients who underwent standard therapy containing anthracyclines, 35 patients who underwent paclitaxel plus trastuzumab (P+TRA group), and 15 patients who underwent trastuzumab monotherapy or no adjuvant therapy; the 5-year invasive disease-free survival rates were 97.8%, 92.9%, and 93.3%, respectively (p=0.255). Adverse events were significantly less frequent in the P+TRA group than that in the standard therapy group. Conclusion: In a real-world setting, de-escalated therapy without anthracyclines demonstrated excellent outcomes similar to the standard therapy containing anthracyclines as well as lower adverse events.