“This platform has no selection bias. Phlebotomy samples are drawn at key decision points. We begin to see that heterogeneity of circulating tumor cells predicted for shorter progression and survival times with selected androgen receptor–directed therapies. We need to study this prospectively,” said formal discussant Oliver Sartor, MD, of Tulane University School of Medicine, New Orleans.

“In a multivariate model, the investigators were able to pick out patients better suited for taxanes. We need to identify the best drugs for specific patients,” he continued.

Dr. Sartor found the information on Type K CTC’s interesting. “There is a lot of meat here. These patients did poorly on all the therapies. This needs further study,” he added.

Therapeutic Potential

“The liquid biopsy of circulating tumor cells described by Dr. Scher is a flexible, powerful technology. There has been much change in the assays in recent presentations, and we now need to ‘lock it’ and see if we can go forward with this version. This dynamic, real-time tracking of heterogeneity using a liquid biopsy can move us forward. It has the potential to help us better evaluate new therapies being considered for individual patients,” Dr. Sartor commented.

In the future, the ability to have biomarker-selected patients could potentially lead to smaller, faster trials of new drugs. “The galeterone phase III trial in men with androgen receptor variant-7–positive metastatic castration-resistant prostate cancer has established this precedent,” he said. ■

Disclosure: Dr. Sartor has been a consultant for Medivation, Janssen, Tokai, and Sanofi.