Efficacy of First-Line Treatment With Pertuzumab and Trastuzumab in Advanced Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer in Routine Clinical Practice.

Background: The first-line treatment for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) involves a combination of trastuzumab, pertuzumab, and a taxane (TPH). This study assessed the efficacy of trastuzumab and pertuzumab (PH) in routine practice, following the treatment protocols of Uruguay's National Resources Fund (FNR), akin to clinical trials. Methods: Patients with advanced MBC treated with PH between 2008 and 2022 per FNR protocols were evaluated. The Kaplan-Meyer method and log-rank test were utilized for analyzing overall survival (OS). Demographic and clinical variables, including age, menopausal status, and hormone receptors (HR), were analyzed. Results: The study included 318 PH-treated patients. The median age was 56 years, with 63.2% being postmenopausal and 60.4% HR and HER-2 positive. With a median follow-up of 17.2 months, the median OS was 29 months. OS varied based on HR status and the presence of metastases at different sites, significantly lower in patients with brain, cutaneous/subcutaneous, and pulmonary metastases. Additionally, OS was higher in patients treated at private institutions compared to public ones. Conclusions: This study demonstrates the disparity in oncological treatment efficacy between clinical trials and clinical reality in Uruguay, emphasizing the importance of authentic environment research for more representative and effective medicine in Latin America.