1657TiP - The STAMPEDE2 stereotactic ablative body radiotherapy (SABR) trial: A phase III, randomised, open-label trial in patients with newly diagnosed oligometastatic prostate cancer (PC) starting androgen deprivation therapy (ADT)

Background

SABR in metachronous oligometastatic PC improves progression-free survival and defers use of systemic therapy. The STAMPEDE2 SABR trial will investigate the addition of SABR to standard of care (SoC) in newly diagnosed synchronous hormone sensitive oligometastatic PC.

Trial design

The STAMPEDE2 trial is a phase III, randomised, open label, multi-centre platform trial testing treatments in metastatic hormone sensitive PC. For the SABR trial, SABR-eligible disease is confirmed on CT/MRI and bone scan and includes: (i) 1 to 5 metastatic lesions in bone and/or non-regional nodes, (ii) all lesions are technically suitable for SABR, (iii) absence of visceral metastases. Patients are randomised with 1:1 allocation to arm A (SoC) or arm S (SoC + SABR). SoC includes long-term ADT, androgen receptor signalling inhibitor (ARSI), prostate (± pelvic nodes) radiotherapy, ± docetaxel as part of triplet therapy. SABR is given in 3 or 5 fractions. PSMA PET/CT and/or whole-body MRI imaging are permitted for SABR planning. Biomarker testing is offered to all eligible patients. Patients with positive biomarker status are offered a second randomisation into the Niraparib trial. Target recruitment is 2476 patients for a target HR of 0.7 for rPFS and 0.75 for OS (90% overall pairwise power). A comprehensive radiotherapy quality assurance programme is implemented. The SABR part of the trial is funded by Cancer Research UK (CRUK), sponsored by University College London (UCL), and co-ordinated by MRC CTU at UCL. Table: 1657TiP