Circulating tumor cell thresholds and survival scores in advanced metastatic breast cancer: the observational step of the CirCe01 phase III trial.

The clinical validity of circulating tumor cell (CTC) count changes during chemotherapy in metastatic breast cancer patients has been validated, but its clinical utility remains to be demonstrated. We report here the non-randomized run-in phase of the CirCe01 trial which was designed to evaluate CTC changes and thresholds to other palliative prognostic scores and establish CTC thresholds to be used in the randomized part of the study. CTC count (CellSearch®) and other prognostic parameters (serum albumin level, lymphocyte level, LDH level, prognostic inflammatory and nutritional index (PINI) and Barbot's score) were assessed in 56 metastatic breast cancer patients before the first cycle of third line chemotherapy. Early changes of CTC count were correlated with treatment outcome. Independent prognostic markers in multivariate analysis were: low serum albumin (HR = 11.1), poor performance status (HR = 3.8), ≥5 CTC/7.5 ml (HR = 3.8) and triple negative subtype (HER2+ and hormone positive vs triple negative: both HR = 0.2). Among patients with ≥5 CTC/7.5 ml at baseline, a composite criteria (<5 CTC/7.5 ml or relative decrease ≥-70% of the baseline CTC count) showed better prognostication for PFS (p=0.002).