Dr Lowentritt on PSA Response and Time to Castration Resistance in mCSPC

Benjamin H. Lowentritt, MD, FACS, director, Minimally Invasive Surgery and Robotics, Chesapeake Urology, discusses prostate-specific antigen (PSA) response and time to castration resistance in patients with metastatic castration-sensitive prostate cancer started on apalutamide (Erleada), enzalutamide (Xtandi), or abiraterone acetate (Zytiga).

PSA90 and time to castration resistance were evaluated in this retrospective, longitudinal descriptive analysis, consisting of data from 95 urology sites in the United States between February 2017 and April 2022. PSA90 was defined as a reduction in PSA of at least 90% from the most recent baseline PSA value in patients with baseline PSA within 13 weeks prior to and including the index date.

The results demonstrated that the rate of PSA90 and time to castration resistance were numerically improved with apalutamide compared with enzalutamide and abiraterone acetate. Specifically, the median time to PSA response was 3.2, 5.2, and 7.6 months with apalutamide, enzalutamide, and abiraterone acetate, respectively. The 1-year PSA90 response rates were 72.3%, 61.6%, and 54.7%, respectively. The median time to castration resistance was not reached with any of the 3 androgen receptor pathways inhibitors. However, additional studies adjusting for baseline characteristics are needed to assess these end points more accurately, Lowentritt says. 

It is important to augment clinical trial data with real-world data because clinical trials are not always representative of patients treated in routine clinical practice, Lowentritt explains. Real-world evidence can also provide a more accurate picture of how therapy is being used in community practices and prove useful in the absence of prospective, randomized, comparative trials, Lowentritt adds.

Findings from this analysis with apalutamide were similar to those seen in the registrational phase 3 TITAN trial (NCT02489318), providing further evidence that these results are attainable in routine clinical practice, Lowentritt concludes.