ASCO GU 2020: Real-World Analysis of Prostate-Specific Antigen Outcomes Among Patients with Metastatic Castration-Resistant Prostate Cancer Treated with Enzalutamide

San Francisco, California (UroToday.com) Most men with advanced prostate cancer will eventually progress to metastatic and non-metastatic castration resistant prostate cancer. Enzalutamide is approved for the treatment of mCRPC and nmCRPC, and more recently, mHSPC as well. There have been only a few real-world studies analyzing PSA outcomes in chemotherapy-naïve men with mCRPC treated with enzalutamide.

The objective of this presented study was to describe PSA response in chemotherapy-naïve men with mCRPC treated with enzalutamide.


This was a retrospective cohort study with data extracted from the Intrinsiq Specialty Solutions (IQSS) urology electronic medical record (EMR) database, which encompasses approximately 30% of all actively practicing private practice urologists in the USA (>1750 physicians from >340 practices from 46 US states). The goal was to analyze the use of enzalutamide by urologists. At the time of study diagnosis enzalutamide was only approved for the treatment of mCRPC. Patients were followed until the end of the study, or until they either were lost to follow-up, or died, or stopped using enzalutamide. Figure 1 demonstrates the study design.

Figure 1: 
ASCO_study_design1.png

The primary endpoint was PSA progression, defined as the time from baseline to the first >25% increase and an absolute increase > 2 ng/dl above baseline or nadir.

The study attrition is shown in Figure 2 and baseline, demographic, and clinical data are shown in Table 1. The median follow-up time was 12.5 (7.6-19.4) months with a median of four PSA tests was observed. The best PSA response are shown in figure 3, demonstrating a median reduction in PSA from baseline of 58% (-89% to 1%), with 14.2% of men reaching an undetectable PSA. 

Figure 2: 
study_attrition.png

Table 1:
 table.png

Figure 3:
figure3.png

The limitations of the study include its retrospective nature, and the fact that the study results are generalizable to chemotherapy naïve patients only with mCRPC in the IQSS database.

This study shows the effectiveness of enzalutamide in chemotherapy naïve mCRPC patients. Interestingly, when compared to the PREVAIL trial1, the median PSA at enzalutamide initiation was lower, which might explain the longer time to PSA progression reported in this study compared to PREVAIL (11.2 months).

Presented by: Stephen Freedland, MD, Cedars-Sinai Medical Center, Los-Angeles, CA, USA

Written By: Hanan Goldberg, MD, Urology Department, SUNY Upstate Medical University, Syracuse, NY, USA, @GoldbergHanan at the 2020 Genitourinary Cancers Symposium, ASCO GU #GU20, February 13-15, 2020, San Francisco, California

References:

  1. Beer TM, Armstrong AJ, Rathkopf DE, et al. Enzalutamide in Metastatic Prostate Cancer before Chemotherapy. New England Journal of Medicine 2014; 371(5): 424-33.
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