Reirradiation Options for Previously Irradiated Prostate Cancer: Is It Feasible to Randomise Between Treatment With Stereotactic Body Radiotherapy (SBRT) Versus High-Dose-Rate Brachytherapy?

Aims Prostate cancer which recurs within the prostate following definitive radiotherapy can be treated again using radiation, known as reirradiation. Systematic reviews of cohort studies of salvage therapies suggest that reirradiation using brachytherapy (BT) or stereotactic body radiotherapy (SBRT) offers favourable disease control with acceptable toxicity. However, the optimal radiotherapy modality in this setting remains to be determined. The study aimed to establish feasibility of randomisation between HDR BT and SBRT. Materials and methods The reirradiation options for previously irradiated prostate cancer (RO-PIP) study is a randomised feasibility study of high-dose-rate BT (HDR BT) or SBRT for locally recurrent prostate cancer. The primary objective was to recruit 60 participants across three centres over a 24-month period. Secondary endpoints include other measures of feasibility, participant-reported outcomes, and clinician-reported acute and long-term toxicity. Results Between October 2022 and May 2025, 60 patients were screened and 18 (30%) were deemed ineligible. Of 42 eligible patients, 23 (54.8%) were randomised to HDR BT (n = 13) or SBRT (n = 10). One randomised participant withdrew prior to commencing treatment. One centre recruited 2 patients and the other centres recruited 9 and 12 patients, respectively. The most common reason for nonparticipation was treatment preference, with 10 patients preferring HDR BT (n = 7), SBRT (n = 2), or androgen deprivation therapy alone (n = 1). Six patients declined to participate for non-disclosed reasons. One patient declined participation due to distance from the treating site, 1 patient declined a biopsy, and 1 patient preferred observation. Conclusion Planned recruitment targets to a randomised multicentre study of BT or SBRT for treatment of locally recurrent prostate cancer were not achieved. A major barrier to participation was patient preference for a specific treatment. Future studies should be designed to allow patient, clinician, and/or centre preference for reirradiation options (either BT or SBRT), which could then be compared to standard of care.