Dr. Dorff on the Importance of Somatic Testing in mCRPC

Tanya B. Dorff, MD, a medical oncologist and associate clinical professor in the Department of Medical Oncology & Therapeutics Research at City of Hope, discusses the importance of somatic testing in metastatic castration-resistant prostate cancer (mCRPC).

On May 15, 2020, the FDA granted rucaparib (Rubraca) an accelerated approval for the treatment of men with BRCA mutation (germline and/or somatic)—associated mCRPC who have been treated with androgen receptor–directed therapy and a taxane-based chemotherapy. On May 19, 2020, olaparib (Lynparza) was approved by the FDA for the treatment of men with deleterious or suspected deleterious germline or somatic homologous recombination repair (HRR) gene–mutated mCRPC who have progressed following prior treatment with enzalutamide (Xtandi) or abiraterone acetate (Zytiga).

Taken collectively, these approvals support the need for somatic testing for men with mCRPC, says Dorff. Although the utility of germline genetic testing had already been solidified in this disease state prior to these approvals, somatic testing is more novel, Dorff explains. As such, the FDA approved the FoundationOne CDx and BRACAnalysis CDx as companion diagnostics to identify patients with mCRPC who harbor HRR gene mutations.

Genomic sequencing can inform which patients are likely to benefit from PARP inhibitors, Dorff says. Moreover, the companion diagnostic is useful because liquid biopsies are more convenient to test patients with bone metastases who may not have tissue available for testing, concludes Dorff.