Prostate cancer (PCa) becomes resistant to androgen ablation through adaptive upregulation of the androgen receptor in response to the low-testosterone microenvironment. Bipolar androgen therapy (BAT), defined as rapid cycling between high and low serum testosterone, disrupts this adaptive regulation in castration-resistant PCa (CRPC).
The TRANSFORMER (Testosterone Revival Abolishes Negative Symptoms, Fosters Objective Response and Modulates Enzalutamide Resistance) study is a randomized study comparing monthly BAT (n = 94) with enzalutamide (n = 101). The primary end point was clinical or radiographic progression-free survival (PFS); crossover was permitted at progression. Secondary end points included overall survival (OS), prostate-specific antigen (PSA) and objective response rates, PFS from randomization through crossover (PFS2), safety, and quality of life (QoL).
The PFS was 5.7 months for both arms (hazard ratio [HR], 1.14; 95% CI, 0.83 to 1.55; P = .42). For BAT, 50% decline in PSA (PSA50) was 28.2% of patients versus 25.3% for enzalutamide. At crossover, PSA50 response occurred in 77.8% of patients crossing to enzalutamide and 23.4% to BAT. The PSA-PFS for enzalutamide increased from 3.8 months after abiraterone to 10.9 months after BAT. The PFS2 for BAT→enzalutamide was 28.2 versus 19.6 months for enzalutamide→BAT (HR, 0.44; 95% CI, 0.22 to 0.88; P = .02). OS was 32.9 months for BAT versus 29.0 months for enzalutamide (HR, 0.95; 95% CI, 0.66 to 1.39; P = .80). OS was 37.1 months for patients crossing from BAT to enzalutamide versus 30.2 months for the opposite sequence (HR, 0.68; 95% CI, 0.36 to 1.28; P = .225). BAT adverse events were primarily grade 1-2. Patient-reported QoL consistently favored BAT.
This randomized trial establishes meaningful clinical activity and safety of BAT and supports additional study to determine its optimal clinical integration. BAT can sensitize CRPC to subsequent antiandrogen therapy. Further study is required to confirm whether sequential therapy with BAT and enzalutamide can improve survival in men with CRPC.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2021 Feb 22 [Epub ahead of print]
Samuel R Denmeade, Hao Wang, Neeraj Agarwal, David C Smith, Michael T Schweizer, Mark N Stein, Vasileios Assikis, Przemyslaw W Twardowski, Thomas W Flaig, Russell Z Szmulewitz, Jeffrey M Holzbeierlein, Ralph J Hauke, Guru Sonpavde, Jorge A Garcia, Arif Hussain, Oliver Sartor, Shifeng Mao, Harry Cao, Wei Fu, Ting Wang, Rehab Abdallah, Su Jin Lim, Vanessa Bolejack, Channing J Paller, Michael A Carducci, Mark C Markowski, Mario A Eisenberger, Emmanuel S Antonarakis
The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD., The Huntsman Cancer Institute, Salt Lake City, UT., The University of Michigan, Ann Arbor, MI., The University of Washington, Seattle, WA., Rutgers University, New Brunswick, NJ., Piedmont Cancer Institute, Atlanta, GA., City of Hope Cancer Center, Duarte, CA., University of Colorado, Aurora, CO., University of Chicago, Chicago, IL., University of Kansas, Kansas City, KA., Nebraska Cancer Specialists, Omaha, NE., University of Alabama at Birmingham, Birmingham, AL., The Cleveland Clinic, Cleveland, OH., The University of Maryland, Baltimore, MD., Tulane University, New Orleans, LA., Allegheny General Hospital, Pittsburgh, PA., Cancer Research and Biostatistics, Seattle, WA.