Objective: To evaluate the efficacy of 1-year adjuvant trastuzumab in Thai patients with HER2-positive early breast cancer. The primary objective was to determine disease-free survival [DFS] and overall survival [OS] during 1 and 2 years.

Materials and Methods: We retrospectively reviewed the medical records of patients with HER2-positive early breast cancer who received standard adjuvant chemotherapy with trastuzumab at
Chulabhorn Hospital between January 2009 and September 2014.

Results: Data of 39 women were available for analysis. Median age was 55 (48 to 60) years. Twenty-seven patients (69.1%) had node-positive disease with median tumor size of 3.0 (0.7 to 12) cm 20 patients also had estrogen receptor-positive disease. Anthracycline-based chemotherapy and taxane were given to 34 and 13 patients, respectively. During median follow-up of 2 years, two patients with recurrence of breast cancer were observed. DFS rate at 1 and 2 years was 97.4% and 93.8%, respectively, whereas OS rate at 2 years was 100%. Unfortunately, congestive heart failure was identified in two patients, with complete recovery after stopping trastuzumab.

Conclusion: Addition of adjuvant trastuzumab in HER2-positive early breast cancer yields a substantial benefit in DFS and OS among the Thai population.

Keywords: HER2-positive early breast cancer, Trastuzumab, Adjuvant therapy, Overall survival