One of the hot topics in the prostate cancer community is the value of detecting AR-V7 tumor cells circulating in the blood. AR-V7 tumor cells in the blood predicts response or failure of treatment with enzalutamide (Xtandi) or abiraterone (Zytiga).
A recent study found that men who have AR-V7 circulating tumor cells in their blood will not respond to Xtandi or Zytiga and will live longer if treated with a taxane based chemotherapy (docetaxel) regimen.
A study in JAMA Oncology, showed that evaluating for the presence of circulating tumor cells (CTCs) with AR-V7 could optimize treatment protocols. The study looked at 161 men with progressing metastatic castration-resistant prostate cancer (mCRPC) and were starting Xtandi, Zytiga or taxane as a first, second or third line treatment. They were evaluated for their sensitivity to Xtandi, Zytiga and chemotherapy using AR-V7 circulating tumor cells in their blood. It was found that .
According to Howard Scher, M.D., chief of the genitourinary oncology services at Memorial Sloane Kettering, “The percentage of men that respond to Xtandi and Zytiga is highest in the first line setting, decreasing steadily as more treatments are given. It was also found that the presence of AR-V7 was able to identify, with specificity, those men who will not benefit from these therapies and should instead start chemotherapy independent of the line of therapy being administered.”
The study showed that men who were AR-V7 positive survived longer when treated with taxane chemo-therapies rather than abiraterone or enzalutamide (median 8.9 vs. 4.6 months).
“This study indicates the potential for an AR-V7 predictive test to enable advanced prostate cancer patients to avoid ineffective therapies and to receive chemotherapy at an earlier stage when it may be more beneficial,” said Murali Prahalad, Ph.D., CEO of Epic Sciences, the owner of the liquid biopsy platform used in the study.
Scher, H et al. Association of AR-V7 on Circulating Tumor Cells as a Treatment-Specific Biomarker With Outcomes and Survival in Castration-Resistant Prostate Cancer. JAMA Oncology. Advance Online Publication: June 4, 2016.