Androgen Deprivation therapy for Oligo-recurrent Prostate cancer in addition to radioTherapy (ADOPT): study protocol for a randomised phase III trial

Background: More than 60% of oligo-recurrent prostate cancer (PCa) patients treated with metastasis-directed radiotherapy (MDRT) develop biochemical recurrence within 2 years. This recurrence rate emphasises the need for improved treatment and patient selection. In line with the treatment of primary PCa, the efficacy of MDRT may be enhanced when combined with androgen-deprivation therapy (ADT). Furthermore, the availability of PSMA PET/CT offers an excellent tool for optimal patient selection for MDRT. This phase III randomised controlled trial will investigate the role of the addition of ADT to MDRT in oligo-recurrent PCa patients selected with PSMA PET/CT to enhance oncological outcome. Methods: Two hundred and eighty patients will be randomised in a 1:1 ratio to the standard treatment arm (MDRT alone) or the experimental arm (MDRT + 6 months ADT). Patients with biochemical recurrence after primary treatment of PCa presenting with ≤ 4 metastases will be included. The primary endpoint is the 2.5-year metastases progression-free survival (MPFS). Secondary endpoints are acute and late toxicity, quality of life, biochemical progression-free survival, overall survival, and the sensitivity of the PSMA PET/CT for detecting oligometastases at low PSA-levels. So far, between March 2020 and December 2021, one hundred patients have been included. Discussion: This phase III randomised controlled trial will assess the possible benefit of the addition of 6 months ADT to MDRT on metastases progression-free survival, toxicity, QoL and survival in PCa patients with 1–4 recurrent oligometastatic lesions. Trial registration: ClinicalTrials.gov, NCT04302454. Registered 10 March 2020.