Observational study of trastuzumab biosimilar in patients with HER2-positive breast cancer under routine clinical practice conditions in Morocco

Trastuzumab, a recombinant humanized monoclonal antibody has demonstrated clinical benefits in women with human epidermal growth factor receptor type 2 (HER2)-positive breast cancer in early and metastatic disease settings. However, real-world data on trastuzumab biosimilars are limited. The primary aim of the HERLife study was to confirm the tolerance of trastuzumab biosimilar from Mylan (Hertraz) in terms of cardiac safety in HER2-positive patients diagnosed with early or metastatic breast cancers under routine clinical practice in Morocco. This was a prospective, non-interventional, multi-center, 12-month follow-up study in adult patients with HER2-positive breast cancer treated with trastuzumab biosimilar. Patients aged ≥ 18 years and with left ventricular ejection fraction (LVEF) ≥ 50% were included. Data on cardiac events, serious or unexpected adverse events (AEs), drug interactions cases, chemotherapy protocols, and response to treatment were collected. In total, 99 patients were included (early breast cancer, n = 70; metastatic breast cancer, n = 29). The median (range) age was 53 (29–76) years. Switching from trastuzumab reference to trastuzumab biosimilar was observed in 32 (32.3%) patients in the overall population, including 45.0% of metastatic breast cancer and 27.0% of early breast cancer patients. Pertuzumab was used in combination with trastuzumab biosimilar in 41.4% and 19.0% of patients in the metastatic and neoadjuvant settings, respectively. Two patients (2.0%) developed an expected AE of a non-significant fall in LVEF, requiring temporary discontinuation of trastuzumab biosimilar for three weeks. No other trastuzumab-related AEs or drug interactions were reported. Four patients (26.7%) had a pathological complete response in the neoadjuvant group (n = 15) over the 12-month follow-up period. Trastuzumab biosimilar was found to have acceptable cardiac safety and a comparable profile of efficacy in HER2-positive breast cancer patients in Morocco.