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Metastasis-directed SBRT for oligometastatic hormone sensitive prostate cancer (METRO): protocol for a prospective
Karin Söderkvist1, Maira Zia2, Adalsteinn Gunnlaugsson3
1Department of Diagnostics and Intervention, Umeå University, Umeå, Sweden. karin.soderkvist@umu.se.
Background:
Metastasis-directed stereotactic body radiotherapy (MD-SBRT) has shown promise in retrospective and phase II studies for oligometastatic hormone-sensitive prostate cancer. However, prospective randomized phase III data-particularly in newly diagnosed cases and in combination with androgen deprivation therapy and next-generation androgen receptor pathway inhibitors-are limited. The METRO trial investigates the addition of MD-SBRT to standard of care in patients with prostate-specific membrane antigen (PSMA) PET/CT-detected oligometastatic disease.
Methods:
METRO is a multicentre, double arm, open-label, phase III randomized trial comparing MD-SBRT plus standard of care versus standard of care alone in patients with one to three PSMA PET/CT-detected distant metastases. The PSMA-RADS scale is used to support inclusion, and only patients with PSMA-RADS 4 or 5 lesions in bone or non-regional lymph nodes are eligible. Standard of care includes time-limited androgen deprivation therapy and/or androgen receptor pathway inhibitor, as well as local radiotherapy to the prostate or prostate bed. Patients are stratified by disease type (synchronous or metachronous) and metastasis location (lymph node/bone). The primary endpoint is biochemical progression-free survival; secondary endpoints include time to castration-resistant prostate cancer, adverse events, and health-related quality of life. The intervention is prescribed either 30 Gy in 3 fractions or 40 Gy in 5 fractions and delivered by stereotactic treatment principles.
Discussion:
The METRO trial investigates the added value of combining MD-SBRT with time-limited intensified hormonal therapy in both synchronous and metachronous oligometastatic hormone-sensitive prostate cancer staged by PSMA‑PET/CT. The use of the PSMA-RADS scale for inclusion ensures a standardized and reproducible approach for patient selection.
Trial Registration:
ClinicalTrials.gov Identifier: NCT04983095.
