102 patients were treated with proton radiation after prostatectomy to the prostate bed or to prostate-bed and pelvic-node. With a median follow-up of 5.5 years, the study reported 5-year biochemical relapse-free and distant metastases-free survival rates were 57% and 97% overall. Acute and late grade 3 or higher genitourinary toxicity rates were 1% and 7%. No patients had grade 3 or higher gastrointestinal toxicity. Acute and late grade 2 gastrointestinal toxicities were 5% and 2%.