Key Biomarkers to Test for in Metastatic CRPC

Fred Saad, MD, FRSC, director of prostate cancer research at Montreal Cancer Institute/CRCHUM, discusses the key biomarkers to test for in patients with metastatic castration resistant prostate cancer.

Testing for these biomarkers is essential as they can be an indicator for benefit of treatment in front line therapy. This was the basis of an analysis of the phase 3 PROpel trial (NCT03732820) that looked at the combination of olaparib (Lynparza) and abiraterone (Zytiga) in this patient population.

With the combination there was a median radiographic progression-free survival (rPFS) of 24.8 months vs 16.6 months for patients on placebo (HR 0.66; 95% CI, 0.54-0.81; P < .0001). Overall survival (OS) reached a 28% maturity rate that favored olaparib and abiraterone compared with placebo (HR 0.86; 95% CI, 0.66–1.12).

A biomarker analysis was conducted to determine if the rPFS and OS would be similar in key biomarker groups, such as PSA or BRCA mutations, and found that patients can do even better in the front line. Saad discusses the key biomarkers they looked at in the analysis and what it means for treatment of this patient population. 

Transcription:

0:07 | The important biomarker to test for is basically PSA, so patients who are on [androgen depravation therapy] progressing defines metastatic castration resistant prostate cancer. That's the most important biomarker, to identify patients who have become metastatic castration resistant. That was the main criteria to get in to the PROpel study; to be metastatic castration resistant, and be progressing, at least PSA-wise, with or without radiographic progression at the time of study entry.

0:43 | Other biomarkers that are of interest are, when we're using a PARP inhibitor, HRR mutations. This includes looking at BRCA mutations, ATM, or all the other list of HRR mutations are important but were not [a part of the] entrance criteria for the PROpel study.