Pelvic nodal recurrences are being increasingly diagnosed in prostate cancer (PCa) patients with the introduction of new molecular imaging techniques, like choline and PSMA PET-CT. At this moment, there are no specific treatment recommendations for patients with limited nodal recurrences and different locoregional treatment approaches are currently being used. The aim of this prospective multicentre randomized controlled phase II trial is to compare metastasis directed therapy (MDT) with elective nodal pelvic radiotherapy (ENRT).
STORM is an international, phase II, open-label, randomised, superiority trial.Patients diagnosed with PET-detected pelvic nodal oligorecurrence (≤5 nodes) following radical local treatment for PCa, were randomized in a 1:1 ratio between arm A: MDT and 6 months of ADT, or arm B: ENRT (25×1.8Gy) with MDT and 6 months of ADT. Patients were stratified by type of PET-tracer (choline or PSMA) and by type of MDT (surgery or radiotherapy). In case of radiotherapy, SBRT (3x10Gy) was used for arm A, with a simultaneous integrated boost in arm B. The primary endpoint is metastasis-free survival and here we report the secondary endpoint acute toxicity, defined as worst grade 2 or more CTCAEv4.0 gastrointestinal (GI) or genitourinary (GU) toxicity, exceeding baseline, up to 3 months after radiotherapy. The chi-square test was used to compare toxicity between treatment arms. This study is registered on ClinicalTrials.gov Identifier: NCT03569241.
Between June, 2018 and April 2021, 196 patients were randomly assigned to MDT or ENRT. 96 of 98 allocated to MDT and 93 of 98 patients allocated to ENRT received at least one fraction of the allocated treatment. Initial treatment at diagnosis was radical prostatectomy in 166 patients (88%) with lymph node dissection in 96 patients (49%). At time of nodal recurrence, the median PSA was 0.97 ng/ml (interquartile range 0.45-2.3). The PET-tracer was choline in 32 (17%) patients and PSMA in 157 (83%) patients. Patients were diagnosed with a single node, 2 nodes or 3-5 nodes in 110 (58%), 49 (26%), 28 (15%) patients (missing information for 2 patients). Surgery was the MDT type of choice in only 11 patients (6%). Worst acute GI toxicity proportions were as follows: grade 2 or higher events in 1 (1%) in the MDT group versus 3 (3%) in the ENRT group (p=0.13). Worst acute GU toxicity proportions were as follows: grade 2 or higher events in 8 (8%) in the MDT group versus 13 (13%) in the ENRT group (p=0.54). Two patients developed a grade 3 event in the ENRT arm (diarrhoea and urinary incontinence with pre-existing grade 2).
Although ENRT treats a more extensive part of the pelvis as compared to MDT, ENRT does not seem to result in a clinically meaningful increase in acute GI or GU toxicity.