Preliminary circulating tumour cell (CTC) analysis in phase II study of weekly cabazitaxel for "unfit" metastatic castration resistant prostate cancer patients (mCRPC) progressing after docetaxel treatment (SOGUG-CABASEM trial).

e16034 Background: Docetaxel (D) is standard first-line chemotherapy in patients (pts) with mCRPC. Cabazitaxel (C), a novel taxane developed to overcome D resistance, showed an overall survival improvement in second line CRPC in a three-weekly dose schedule. We aimed to evaluate efficacy and safety of weekly C/prednisone in unfit mCRPC previously treated with D. Possible relation of CTC counts and its early response with efficacy is analyzed. Methods: Unfit pts (ECOG 2, dose reduction due to febrile neutropenia during treatment with D or radiation therapy affecting more than 25% of bone marrow reserve) with mCRPC progressing after D treatment with adequate bone marrow, liver and kidney functions were included. C 10 mg/m2 was administered on days 1, 8, 15 and 22 of 5-week cycles with daily prednisone 5 mg b.i.d. Radiological and PSA response was evaluated according to the PCCTWG II criteria. CellSearch system was used for counting the CTC. CTC cut-off basal levels: u003e=5 cells/7.5mL (A) / u003c5 cells/7.5mL (B...