Salvage hypofractionated accelerated versus standard radiotherapy for the treatment of biochemical recurrence after radical prostatectomy (SHARE): the protocol of a prospective, randomized, open-label, superiority, multi-institutional trial

Background: While several phase III trials have investigated the role of hypofractionated radiotherapy in the definitive treatment of localized prostate cancer, prospective data reporting the outcomes of hypofractionated radiotherapy in the postoperative treatment setting are sparse. Therefore, this study is designed to assess the efficacy and treatment-related toxicity of hypofractionated salvage radiotherapy for the treatment of biochemical recurrence in men who underwent radical prostatectomy. The primary objective of this trial is to investigate whether hypofractionated radiotherapy improves biochemical control compared with conventionally fractionated radiotherapy. In addition, treatment-related toxicity, quality of life, and survival will be evaluated as secondary endpoints. Methods: In this prospective, randomized, multi-institutional trial (the SHARE study), patients with intermediate- or high-risk prostate cancer will be randomized to receive either hypofractionated radiotherapy (65 Gy in 2.5-Gy fractions) or conventionally fractionated radiotherapy (66 Gy in 2-Gy fractions). Prostate bed irradiation or elective pelvic nodal irradiation including the prostate bed will be performed using intensity-modulated radiotherapy and daily image guidance. Treatment efficacy will be assessed using the serum tumor marker prostate-specific antigen, and toxicity will be evaluated through both physician- and patient-reported outcomes. Quality of life will also be investigated. Discussion: This study is designed to demonstrate whether hypofractionated radiotherapy is beneficial in terms of biochemical control and toxicity compared with standard salvage radiotherapy. If hypofractionated radiotherapy is shown to be superior to conventionally fractionated radiotherapy, it will mean that improved biochemical control can be achieved, accompanied by greater patient convenience and more efficient use of medical resources. Trial registration: ClinicalTrials.gov NCT03920033.