Treatment with antiandrogen therapy is a standard of care for men with prostate cancer receiving salvage radiotherapy following postsurgical biochemical recurrence. This standard, based in part on results from the randomized phase III RTOG 9601 trial, found that the addition of 2 years of antiandrogen therapy to postoperative radiotherapy resulted in a significant improvement in overall survival (OS). However, at the 2019 American Society for Radiation Oncology (ASTRO) annual meeting, Daniel Spratt, MD (University of Michigan Rogel Cancer Center, Ann Arbor, Michigan), presented results from a subset analysis of this trial that showed a decrease in OS in some patients receiving long-term hormone therapy (LBA1).
The RTOG 9601 trial evaluated postoperative radiation therapy plus or minus bicalutamide (150 mg/day) for 2 years in 760 men with recurrent prostate cancer. This subset analysis evaluated outcomes in patients based on prostate-specific antigen (PSA) levels prior to salvage radiotherapy to determine if PSA level could be used to identify which patients are most likely to benefit from long-term antiandrogen treatment. In patients with PSA levels greater than 1.5 ng/mL, OS was significantly improved with antiandrogen therapy (HR 0.45, P = .02). However, in patients with PSA levels less than 1.5 ng/mL, there was no OS benefit for bicalutamide treatment (HR 0.87). In patients with PSA levels of 0.6 ng/mL or lower, addition of bicalutamide to salvage radiotherapy decreased OS. In patients with the lowest PSA levels, 12-year estimates for other-cause mortality were increased from 10% without bicalutamide to 19% with bicalutamide (HR 1.94, P = .009). This group was also 3 to 4 times more likely to experience severe cardiac events and neurologic problems.
Dr Spratt concluded that long-term antiandrogen treatment is not a “one size fits all” treatment approach and appropriate use of hormone therapy should be determined in a patient personalized manner. In particular, these data support PSA level as a predictive biomarker to determine which patients are most likely to benefit from hormone therapy. The BALANCE trial, which is currently enrolling, will use genetic testing to further evaluate which patients are most likely to benefit from hormone therapy.
For more information about this study, visit Medscape Medical News.