Circulating tumor cells as a prognostic marker for efficacy in the randomized phase III JO21095 trial in Japanese patients with HER2-negative metastatic breast cancer

Purpose Prognostic effects of circulating tumor cells (CTCs) have been reported in metastatic breast cancer (MBC). However, few phase III trials have investigated the potential role of CTCs in treatment selection. We explored potential relationships between CTCs, efficacy, and differential treatment effects.