Abstract 365P
Background
The current standard of care for metastatic hormone-sensitive prostate cancer (mHSPC) is androgen deprivation + systemic therapy. Oligometastatic HSPC, however, represents a unique disease entity following the STAMPEDE trial, where de novo mHSPC patients with a CHAARTED-defined low disease burden (DN-mHSPC-LV) had a hazard ratio of death of 0.68 after prostate radiotherapy (PRT). Despite the SABR-COMET results of a survival benefit with stereotactic RT on metachronous oligometastatic sites of predominantly prostate patients, radical RT (RRT) in DN-mHSPC-LV has not been studied. This study analysed the outcomes of such patients receiving RRT to all disease sites vs PRT alone.
Methods
DN-mHSPC-LV receiving RRT to the prostate and all oligometastatic sites (Arm A) vs PRT alone (Arm B) in a Hong Kong tertiary hospital between 1st January 2018 and 31st December 2021 were reviewed. Outcomes of failure-free survival (FFS), progression-free survival (PFS), overall survival (OS) and treatment-related toxicity were analysed using the multivariable Cox-proportional hazards model.
Results
38 eligible patients (25 in Arm A & 13 in Arm B) were identified. The median numbers of oligometastatic sites were 1 in Arm A and 2 in Arm B. The median Gleason score was 8 in both arms. T/N/M staging was mostly balanced but more patients in Arm A had M1b vs M1a disease. Median presenting PSA (ng/mL) was higher in Arm A (59) than Arm B (20). Arm A received up to 76Gy/38# to the prostate + a boost of up to 67.5Gy or stereotactic RT to the oligometastatic sites. Arm B received 55-60Gy/20# to the prostate alone. Systemic treatments were balanced. Median follow up was 55.1 months and 34.8 months in Arms A and B, respectively. Median FFS was 49 months and 33.1 months in Arms A and B, respectively (P = 0.0317; HR 0.134; 95% CI 0.021-0.839). Median PFS was 49 months in Arm A vs 25.8 months in Arm B (P = 0.0228; HR 0.17, 95% CI 0.037-0.781). OS data were not yet mature and there was no difference in TrT between the arms.
Conclusions
To our knowledge, this is the first study comparing RRT against PRT in DN-mHSPC-LV. RRT was well tolerated. FFS and PFS are significantly longer with radical vs palliative treatment . FFS is an established surrogate for OS in prostate cancer. This study thus justifies prospective studies on RRT for DN-mHSPC-LV.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.