A Phase I Trial of Neoadjuvant Stereotactic Body Radiotherapy Prior to Radical Prostatectomy for Locally Advanced Prostate Cancer

Abstract

Men with locally advanced prostate cancer who undergo radical prostatectomy (RP) often develop recurrence and require postoperative radiotherapy. We aimed to determine the safety of neoadjuvant stereotactic body radiotherapy (SBRT) before RP in this population. A single-institution phase 1 trial (NCT02946008) of men with high-risk or node-positive prostate cancer were enrolled between March and October 2017. The primary endpoint was to determine the maximum tolerated dose of SBRT based on a composite 30-day post-RP toxicity goal of ≤28% of patients experiencing a dose-limiting toxicity (DLT). Secondary outcomes included toxicity, efficacy, and multiple quality of life (QoL) inventories. SBRT (30-35 Gy/5 fractions) was delivered to the prostate and seminal vesicles, and 25 Gy/5 fractions to the pelvic lymph nodes. RP was performed for a median of 6 weeks post-SBRT. Hormone therapy was not allowed. Median follow-up was 40 months (range, 33-44). Twenty-five percent of the patients (n=4) experienced a DLT within 30 days post-RP; however, the trial was stopped early (n=16 of planned 38 patients) owing to the proportion and severity of the late adverse events. Post-RP grade 3 genitourinary and gastrointestinal toxicities occurred in 75% (n=12) and 25% (n=4) of patients, respectively. Two patients required cystectomy and urinary diversion ≥2 years post-RP. At 24 months post-RP, 75% (n=12) of men used ≥1 pad/d and 0% had erections suitable for intercourse. Surgical margins were negative in all patients and 31% (n=5) had complete or partial (pre-RP) MRI-response to SBRT. Three-year biochemical recurrence and distant metastasis were 45% (95% CI, 5%-68%) and 28% (95% CI, 0%-49%), respectively. Neoadjuvant SBRT followed by RP resulted in unacceptably high toxicity and severe QoL declines.