Benefit of prostate radiotherapy for patients with lymph node only or < 4 bone metastasis and no visceral metastases: Exploratory analyses of metastatic site and number in the STAMPEDE “M1|RT comparison”

Abstract

Abstract Background Prostate radiotherapy (PRT) with androgen deprivation therapy (ADT) is now recommended as a first line option for de-novo low burden metastatic prostate cancer. In the STAMPEDE “M1|RT comparison” metastatic burden was a determinant of benefit, based on pre-specified prognostic criteria. We have now performed exploratory analyses of metastases as defined by site and number to improve prediction of treatment benefit from PRT. Methods Patients (pts) randomized to the ADT (± docetaxel) vs PRT + ADT (± docetaxel) were studied. Metastatic site, distribution and number were evaluated based on conventional imaging and used to explore treatment effects to refine the metastatic burden definition. Results focused on the trial’s key outcome measures: overall (OS) & failure-free survival (FFS), analysed using standard survival analysis methods. HR\xa0 Results Following exclusions (imaging unavailable for central review, n\xa0=\xa0122), 1939 pts randomized in “M1|RT comparison” were included. Of these, 181 pts had only lymph node (LN) mets, 1587 had bone (±LN) mets and 171 had other visceral mets (±bone/LN). Baseline characteristics such as age (median 68 years), PSA (median 98\xa0ng/ml) were balanced between the arms. In LN only pts, PRT improved OS (HR\xa0=\xa00.62, 95%CI 0.35-1.09) & FFS (HR\xa0=\xa00.64, 95%CI 0.43-0.96). In bone (±LN) pts with 0.1) for baseline factors such as age, N stage, Gleason score, RT schedule or docetaxel use. Conclusions Prostate RT + ADT (± docetaxel) improved OS & FFS in pts with only LN or\xa0 Clinical trial identification NCT00268476. Legal entity responsible for the study Medical Research Council-Clinical Trials Unit and University of Manchester. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.