Circulating tumor cells as a biomarker predictive of sensitivity to docetaxel chemotherapy in patients with castration-resistant prostate cancer.

AIM: We examined whether Circulating Tumor Cells (CTCs) can be used to predict survival in patients with bone-metastatic castration-resistant-prostate cancer (mCRPC) treated with docetaxel chemotherapy.

PATIENTS AND METHODS: All patients with mCRPC who had experienced treatment failure with androgen deprivation therapy and had received docetaxel chemotherapy were eligible for study inclusion. CTCs in whole blood were enumerated with the CellSearch System.

RESULTS: The median CTC count at baseline before starting trial treatment was 7 (range=0-227) CTCs per 7.5 ml blood. Out of the 57 patients, 24 (42.1%) had a CTC count of less than 5, while 27 patients (47.4%) had a CTC count of 5-50 and six patients (10.5%) had a CTC count of more than 50. A threshold of 5 or more CTCs per 7.5 ml blood was used to assess the ability to predict survival. The patient charts were examined to determine the median overall survival time, which ranged from 6 to 37 months (mean=12.8±8.1 months, median=15.3 months). Thirty-three patients (57.9%) had 5 or more CTCs before docetaxel chemotherapy, with a median overall survival of 10.5 months compared to 25.0 months for 24 patients (42.1%) with fewer than 5 CTCs (p<0.001). CTC and alkaline phosphatase (ALP) were independent predictors of overall survival time (p=0.004, and p=0.023, respectively). In addition, poorer overall survival was predicted by a CTC count of 5 or more after three courses of docetaxel chemotherapy.

CONCLUSION: The CTC count may be an independent predictor of overall survival in patients with mCRPC treated with docetaxel chemotherapy. The numbers of CTCs detected was important in assessing response to chemotherapy and predict disease outcome.