SBRT and HDR brachytherapy produce lower PSA nadirs and different PSA decay patterns than conventionally fractionated IMRT in patients with low- or intermediate-risk prostate cancer

Stereotactic body radiation therapy and HDR brachytherapy produce lower nPSAs than IMRT. Within 1000 days of follow-up, the modalities produce similar rates of PSA decay; subsequently, decay continues (albeit at a slower pace) after SBRT and HDR brachytherapy but plateaus with IMRT. Because nPSA is a validated predictor of long-term outcome, these data not only suggest a distinct radiobiological effect with SBRT and HDR brachytherapy, but also predict for clinical outcomes that might equal or surpass those of IMRT.