Dr. Hussain on Rationale to Explore Relationship Between PSA and Outcomes in Nonmetastatic CRPC

Maha Hussain, MD, FACP, FASCO, Genevieve E. Teuton Professor of Medicine in the Division of Hematology and Oncology of the Department of Medicine, and the deputy director of the Robert H. Lurie Comprehensive Cancer Center of the Northwestern University Feinberg School of Medicine, discusses the design of the phase 3 PROSPER trial in patients with nonmetastatic castration-resistant prostate cancer (CRPC).

Updated results from the PROSPER trial were presented during the 2020 ESMO Virtual Congress, says Hussain. In the phase 3 trial, patients with nonmetastatic CRPC were randomized 2:1 to receive either enzalutamide (Xtandi) or placebo. At the time of disease progression, patients were unblinded and permitted to receive alternative treatments, according to Hussain.

The updated data focused on whether benefit with enzalutamide can be predicted at an individual patient level, Hussain adds. When clinical trials are conducted, they’re done in groups of patients; however, each and every patient case is distinct. One cannot assume that if 1patient experienced benefit with a treatment that another patient will also experience benefit, notes Hussain. Additionally, it is important to be mindful of how frequently patients will be subjected to imaging because of the associated physical and monetary costs.

This research builds on data from another phase 3 clinical trial that examined the nadir prostate-specific antigen (PSA) and its association with outcomes in terms of overall survival and metastasis-free survival. In the context of metastatic disease, it was demonstrated that a decreased and maintained PSA at a certain low level can predict for better outcomes, adds Hussain. When a tumor responds, that is better than a tumor that is not responding. Essentially, a similar trend was demonstrated in PROSPER, concludes Hussain.