ASCO GU 2018: Pembrolizumab for Recurrent or Advanced Prostate Cancer
Methods:
Fifty-four consecutive men with recurrent or advanced prostate cancer were treated with 1 to 9 cycles of Pembro 200 mg every 3 weeks with or without SBRT at a private medical oncology clinic. Charts were retrospectively reviewed for response and toxicity. Definitions: Response (R) = >50% PSA decline; Progressive Disease (PD) = >50 % PSA increase. Stable Disease (SD)= neither response or progression.
Results:
43 men completed 3 cycles of Pembro and were evaluable for toxicity. Toxicity was comparable to reports of other cancers besides PC, with 30.2% (13/43) having Grade 2 or higher toxicity. 31 men completed 4 cycles of Pembro and were evaluable for response. For the 31, the median Gleason score was 4+4=8. Treatment prior to Pembro was enzalutamide (26), abiraterone (18), and sipuleucel-t (23) and docetaxel (20). All but 4 men were castrate resistant (CRPC). Ten men got SBRT to a metastasis shortly before or during Pembro. Number of mutations were determined by the Guardant 360 assay. 17/31 (55%) were responders (19%) or had stable disease (35%). Characteristics of the two subgroups, R (6/31) + SD (11/31) versus PD (14/31), are presented in the table.
Conclusions:
Disease stabilization or response occurred in slightly more than half of the men treated with 4 or more cycles of Pembro. These positive responses were more common in men with lower PSA, fewer bone mets, fewer mutations, less proportion of previous chemotherapy, and there was a trend toward greater benefit in castrate sensitive disease and older men.
Presented by: Juliana Higa, Los Angeles, CA, USA
Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA