Palbociclib and trastuzumab for HER2-positive metastatic breast cancer: final overall survival results of cohort A and B of SOLTI-1303-PATRICIA trial

Abstract

Background: The SOLTI-1303-PATRICIA trial (NCT02448420) is a phase II study investigating palbociclib and trastuzumab, with or without endocrine therapy, in hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). This manuscript presents final overall survival (OS) results and biomarker analyses. Patients and methods: Patients previously treated with trastuzumab and two to four regimens were eligible. For estrogen receptor (ER)-negative disease (cohort A), patients received palbociclib and trastuzumab. For ER-positive disease, patients were randomized 1 : 1 to cohort B1 (no additional therapy) or B2 (letrozole). OS and long-term progression-free survival (PFS) were pre-defined secondary endpoints. Kaplan—Meier curves and stratified Cox models were used. Results: Among 71 patients, median OS was 29.8 months [95% confidence interval (CI) 20.9-38.0 months]; 4-year OS rates were 13.3% (A), 35.7% (B1), and 32.3% (B2). PAM50 luminal subtypes showed better OS than non-luminal subtypes (38.0 versus 26.6 months). Exploratory biomarker analyses found luminal-related genes associated with better long-term survival, while basal and proliferation-related genes were linked to resistance. Higher luminal A, luminal B, and previously reported chemo-endocrine scores correlated with favorable prognoses. Conclusions: These findings highlight the relevance of gene expression profiling in HER2-positive breast cancer and support biomarker-driven patient selection. Long-term PATRICIA results validate the potential of non-chemotherapybased approaches in HR-positive/HER2-positive MBC.