Mutations and Overall Survival on Fulvestrant versus Exemestane in Advanced Hormone Receptor-Positive Breast Cancer: A Combined Analysis of the Phase III SoFEA and EFECT Trials.

Purpose: mutations are acquired frequently in hormone receptor-positive metastatic breast cancer after prior aromatase inhibitors. We assessed the clinical utility of baseline circulating tumor DNA (ctDNA) analysis in the two phase III randomized trials of fulvestrant versus exemestane.

Experimental Design: The phase III EFECT and SoFEA trials randomized patients with hormone receptor-positive metastatic breast cancer who had progressed on prior nonsteroidal aromatase inhibitor therapy, between fulvestrant 250 mg and exemestane.