Efficacy of adjuvant combination therapy with trastuzumab and chemotherapy in HER2-positive early breast cancer: A single institutional cohort study from clinical practice

Background/Aim: To evaluate the improvement in the prognosis by adjuvant trastuzumab in clinical practice and the risk factors for distant recurrence, we retrospectively investigated the prognosis of HER2-positive early breast cancer in our department before and after the introduction of adjuvant trastuzumab. Patients and Methods: Cohorts A and B included 161 and 182 cases, respectively, who underwent surgery before (2000-2007) and after (2008-2015) the introduction of adjuvant trastuzumab. Results: The rates of relapse-free and distant metastasis-free survival were significantly better in cohort B than in cohort A. The risk factors of distant recurrence found in cohort A, such as the presence of lymph node metastasis, lymphatic invasion, and a low histological grade, did not increase the risk in cohort B. Conclusion: Many risk factors seemed to have been negated by adjuvant trastuzumab administration. Therefore, further escalation of adjuvant treatment should be carefully considered.