LAUSR

Abstract Deciding if patients with small (≤1 cm), node-negative, human epidermal growth factor receptor 2 (HER2) positive breast cancer should receive adjuvant systemic therapy remains a challenge. No randomized clinical trials have examined the efficacy of trastuzumab in this setting. This prospective observational study aimed to investigate the choice of adjuvant systemic therapy in clinical practice in China. We prospectively collected data from patients with HER-2 positive breast cancer (less than 1 cm and node negative) patients who underwent breast cancer surgery at Shanxi Provincial People's Hospital Breast Center from January 1, 2017 to December 31, 2019, and retrospectively investigated the association between baseline clinicopathological features and treatment strategy, cardiotoxicity, and disease outcome. Of 168 eligible patients, 102 (60.7%) received adjuvant systemic therapy with trastuzumab (AST+T), 47 (28%) received adjuvant systemic therapy without trastuzumab (AST) and 19 (11.3%) did not receive adjuvant systemic therapy. Multivariate logistic regression analysis demonstrated that age, tumor size and hormone receptor status were significantly associated with treatment choice. Three-year invasive disease-free survival probability was 100%, 97.9% and 89.5% with AST+T, AST, and no therapy, respectively (P < .001). The majority of patients (60.7%) with pT1a-b pN0 HER2 positive breast cancer received adjuvant systemic therapy with trastuzumab, whereas only 11.3% did not receive any adjuvant systemic therapy. Tumor size, age and hormone receptor status influenced treatment choice. The 3-year invasive disease-free survival probability was significantly higher for patients who received adjuvant systemic therapy with trastuzumab compared with those who did not receive adjuvant systemic therapy. Cardiac adverse events were rare.