San Diego, CA USA (UroToday.com) A presentation in today’s Prostate Cancer: Advanced (including Drug Therapy) III session at the AUA 2016, described long term follow-up of circulating tumor cells (CTC) predictors for survival in men treated with abiraterone for mCRPC following chemotherapy.
Dr Christian Meyer reviewed that Circulating tumor cells (CTC) are established biomarkers able to predict response to chemotherapy (CTX) in metastatic castration resistant prostate cancer (mCRPC). In the COU-AA-301 trial cohort, a biomarker panel that include CTC was shown to be predictive of survival in men treated with abiraterone acetate after chemotherapy.
The authors enrolled 37 patients with mCRPC who progressed after at least one but not more than two prior chemotherapy regimens. Treatment included AA 1000mg daily plus prednisone 5mg BID and was continued until disease progression was identified or unacceptable toxicity. A full blood Cell save tube was drawn when patients were included in the study. Evaluation of CTC was performed according to the Cell Search Epithelial Cell Test protocol (Veridex, Raritan, NJ). Subsequent CTC measurements were done monthly on each follow-up visit.
Kaplan-Meier (KM) estimates and Cox regression analysis assessed the influence of independent predictors on overall survival. Mean patient age was 71.3 years, median PSA was 297 ng/ml and 20% and 8% of the patients had significant pain and visceral metastasis respectively. After a median (IQR) follow-up of 17.7 (9.4 – 31.9) months, 35 of 37 patients died. PSA declined by 30% and 50% in 45% and 37% of the patients.
A significant survival benefit was shown for patients with CTC counts <5 vs. >5 (p<0.001). Baseline PSA, hemoglobin, time under AA, number of systemic therapies after AA, discontinuation and CTC converters were significant predictors of OS on the univariable analysis. However, only time of treatment under AA and number of subsequent treatment lines (e.g. Enzaltuamid, Radium-223, Cabazitaxel) after AA were identified as independent predictors of overall survival on multivariable analysis.
The authors conclude that CTC >5 is an early indicator of disease progression. CTC counts failed to have significant association with OS in a multivariate context. Access to subsequent therapies provides proven survival benefit for men with mCRPC after chemotherapy and AA.
Presented By: Christian Meyer, MD
Written By: Miki Haifler MD. Fox Chase Cancer Center, Philadelphia, PA. at the 2016 AUA Annual Meeting - May 6 - 10, 2016 – San Diego, California, USA