Study protocol on quality of life and erectile function recovery in unfavorable intermediate-risk prostate cancer:...

In unfavorable intermediate-risk prostate cancer, radiotherapy plus androgen deprivation therapy (ADT) is standard, but GnRH agonists can cause testosterone flare and delayed hormonal recovery, negatively affecting erectile function (EF) and quality of life (QoL). Relugolix, an oral GnRH antagonist, enables rapid testosterone suppression and faster recovery after discontinuation. The REDI-CaP trial investigates whether combining Relugolix with high-precision stereotactic body radiotherapy (SBRT) aims to improve EF recovery while evaluating whether cancer control is maintained.REDI-CaP is a prospective, single-arm, single-center Phase II study enrolling 55 patients (accounting for an anticipated 10% attrition rate, to yield 50 evaluable patients for the primary analysis). Participants receive Relugolix 120 mg daily for 6 months (AIFA-approved off-label use). SBRT is delivered with the CyberKnife system (36.25 Gy in 5 fractions) during the fourth month of ADT. The primary endpoint is EF recovery 6 months after ADT cessation, defined as an IIEF-5 score >17 or an increase of ≥5 points from baseline. Secondary endpoints include biochemical progression-free survival, acute and late toxicity, and patient-reported outcomes.Approved by the Institutional Ethics Committee; conducted according to ICH-GCP and the Declaration of Helsinki.The REDI-CaP trial is designed to investigate whether integrating pharmacology with advanced radiotherapy can help preserve patients' quality of life while assessing cancer control outcomes.Clinical Trial Registration: www.clinicaltrials.gov identifier is NCT07302451 and EU CT 2025-521170-33-00.