Two-center phase 2 study of patient-reported outcomes with stereotactic body radiotherapy after radical prostatectomy

Postoperative radiotherapy remains underused for men with biochemical recurrence or adverse pathological features after radical prostatectomy (RP) for prostate cancer. The phase 2 SCIMITAR trial, at two centers in Los Angeles, investigated physician-reported toxic effects and patient-reported outcomes (PROs) following prostate bed stereotactic body radiotherapy (SBRT) after RP. In this nonrandomized trial including 100 patients, late grade 2 and 3 genitourinary toxic effect rates were 25% and 4%, respectively, and late grade 2 and 3 gastrointestinal tract toxic effect rates were 3% and 3%, respectively. Compared with conventionally fractionated radiotherapy (CFRT), the adjusted odds ratio for SBRT causing decrements in PROs more than 2-fold the threshold for mininal clinically important difference were 1.55 (p=0.14) for urinary incontinence, 0.94 (p=0.87) for urinary irritation, and 1.03 (p=0.93) for bowel function. The authors conclude that in this trial, post-RP SBRT was well-tolerated, with no measurable different declines in urinary or bowel PROs compared with CFRT.