Retrospective evaluation of demografic and clinicopathological characteristics of adjuvant T-DM1 use in patients with HER2-pozitive breast cancer

Retrospective evaluation of demographic and clinicopathological characteristics of adjuvant T-DM1 use in patients with HER2-positive breast cancer AIM: Breast cancer is the most common cancer among women worldwide and remains the leading cause of cancer-related deaths. Approximately 20-25% of cases are HER2 positive, often indicating aggressive disease. There is little data regarding the use of trastuzumab emtansine in early-stage HER2 positive breast cancer patients. This study aims to evaluate the demographic and clinicopathological characteristics of patients receiving trastuzumab emtansine. MATERIALS AND METHODS: Patients with stage I-II HER2-positive breast cancer who presented to the Medical Oncology Department of Sakarya Training and Research Hospital between 2019 and 2024 were included. Data regarding age, menopausal status, receipt of neoadjuvant chemotherapy, surgery type, residual tumor or lymph node involvement, radiotherapy, recurrence or progression during follow-up, adverse events during trastuzumab emtansine treatment, histological grade, Ki-67 and Miller-Payne response were collected and analyzed in comparison with real-world data. RESULTS: 30 patients were included in the study. The mean age was 50; one-third were pre- or perimenopausal, and more than half, postmenopausal. Invasive ductal carcinoma was the most common histology. Neoadjuvant chemotherapy regiments including trastuzumab, pertuzumab, and anthracycline/taxane combinations. Breastconserving surgery and sentinel lymph node dissection were most common. MillerPayne grade 3 was the most frequent response. Most frequent adverse events were thrombocytopenia, neutropenia, and elevated transaminases CONCLUSION: Our findings support the efficacy and safety of chemotherapy protocols containing trastuzumab ± pertuzumab, as well as the clinical use of targeted therapies such as adjuvant T-DM1. Future studies should investigate the long-term outcomes of different molecular subgroups and platinum-based treatments in larger patient cohorts. Keywords: Breast cancer, chemotherapy, trastuzumab emtansine