Abstract 2410: Circulating tumor cells to guide the choice between chemotherapy and hormone therapy as first line treatment for metastatic breast cancer patients: the STIC CTC METABREAST trial

Background Baseline CTC count already demonstrated its very good performance as an independent prognostic marker in metastatic breast cancer (MBC), before the start of any treatment (Cristofanilli, NEJM 2004; Pierga Ann Oncol 2011). Multivariate analyses performed in both a pooled analysis (Liu, ASCO 2011) and in the IC 2006-04 study showed that the other independent prognostic factors were the performance status and hormone-receptor (HR) status. Oppositely, the other criteria that are frequently used to choose between hormone therapy and chemotherapy for the treatment of first line hormone receptor-positive MBC patients (e.g. metastatic sites, metastasis-free interval…) were not independent prognostic factors. On the basis that CTC count may be a better criterion for this important choice than the currently used empiric criteria, we designed a large pivotal phase III trial. Methods N=996 HR+ M+ breast cancer patients will be randomized between the clinician choice and CTC count-driven choice. Main inclusion criteria include hormone receptor-positive MBC patients with no previous treatment for the metastatic disease, and who can receive either hormone therapy or chemotherapy as first line treatment. In the CTC arm, patients with ≥5 CTC/7.5ml will receive chemotherapy whereas patients with