Response to Induction Neoadjuvant Hormonal Therapy Using Upfront 21-Gene Breast Recurrence Score Assay-Results From the SAFIA Phase III Trial

PURPOSE Luminal, human epidermal growth factor receptor 2-negative breast cancer represents the most common subtype of breast malignancies. Neoadjuvant strategies of operable breast cancer are mostly based on chemotherapy, whereas it is not completely understood which patients might benefit from neoadjuvant hormone therapy (NAHT). MATERIALS AND METHODS The SAFIA trial is a prospective multicenter, international, double-blind, neoadjuvant phase III trial, using upfront 21-gene Oncotype DX Breast Recurrence Score assay (recurrence score [RS] < 31) to select operable luminal human epidermal growth factor receptor 2-negative patients, for induction hormonal therapy HT (fulvestrant 500 mg with or without goserelin) before randomly assigning responding patients to fulvestrant 500 mg (with or without goserelin) plus either palbociclib (cyclin-dependent kinase 4/6 inhibitor) or placebo. The objectives of this interim analysis were to assess the feasibility of upfront RS determination on core biopsies in the Middle-East and North Africa region and evaluate the efficacy of induction NAHT in patients with an RS < 31. RESULTS At the time of this interim analysis, 258 patients with relative risk were accrued, including 202 patients (RS < 31% to 78.3%) treated with induction NAHT and 182 patients evaluable so far for response. The feasibility of performing the Oncotype DX assays on core biopsy specimens was optimal in 96.4% of cases. Overall, 93.4% of patients showed hormone sensitivity and no difference in NAHT efficacy was noticed between RS 0-10, 11-25, and 26-30. Interestingly, patients with high RS (26-30) showed a trend toward a higher major response rate (P = .05). CONCLUSION The upfront 21-gene assay performed on biopsies is feasible in our population and has allowed us to select patients with high hormone sensitivity (RS < 31). This approach could be an alternative to upfront surgery without significant risk of progression, particularly during pandemic times. (C) 2021 by American Society of Clinical Oncology