ASCO Expert and GU News Planning Team Member, Charles Ryan, MD, of the University of California, San Franciso, Helen Diller Family Comprehensive Cancer Center, said the results presented by Singh et al at the 2015 Genitourinary Cancers Symposium were “encouraging” and that it makes sense to exploit two complementary arms of the immune system: The vaccine initiates or “jump starts” response to the tumor, and then active immunotherapy enhances the durability of response.

Dr. Ryan noted that the Halabi nomogram was developed before the availability of newer therapies like abiraterone (Zytiga) and enzalutamide (Xtandi), so projected survival using that nomogram is probably not applicable in the modern era.

The rilimogene galvacirepvec/rilimogene glafolivec (Prostvac) vaccine has several potential advantages over sipuleucel-T (Provenge), Dr. Ryan commented. “Prostvac is off the shelf, whereas sipuleucel-T relies on harvesting enough of the patient’s own immune cells. Thus, there is greater potential for a uniform product with Prostvac,” he said. “It is also possible that Prostvac will be less expensive, but that [remains to be seen].”

Regarding the approach of combining the new vaccine with anti–PD-L1, Dr. Ryan said it is possible that an anti–PD-L1 agent would be safer than ipilimumab (Yervoy), “but this would require further validation in prostate cancer. Ipilimumab is better studied in prostate cancer than anti–PD-L1.” ■

Disclosure: Dr. Ryan reported no potential conflicts of interest.