Impact of prostate radiotherapy on survival outcomes in clinically node-positive prostate cancer: A multicentre retrospective analysis

Purpose To evaluate clinical outcomes for cN1M0 prostate cancer treated with varied modalities. Materials and methods Men with radiological stage cN1M0 prostate cancer on conventional imaging, treated from 2011-2019 with various modalities across four centres in the UK were included. Demographics, tumour grade and stage, and treatment details were collected. Biochemical and radiological progression-free survival (bPFS, rPFS) and overall survival (OS) were estimated using Kaplan Meier analyses. Potential factors impacting survival were tested with univariable log-rank test and multivariable Cox-proportional hazards model. Results Total 337 men with cN1M0 prostate cancer were included, 47% having Gleason grade group 5 disease. Treatment modalities included androgen deprivation therapy (ADT) in 98.9% men, either alone (19%) or in combinations including prostate radiotherapy (70%), pelvic nodal radiotherapy (38%), docetaxel (22%), or surgery (7%). At median follow up of 50 months, 5-year bPFS, rPFS, and OS were 62.7%, 71.0%, and 75.8% respectively. Prostate radiotherapy was associated with significantly higher bPFS (74.1% vs 34.2%), rPFS (80.7% vs 44.3%) and OS (86.7% vs 56.2%) at five years (log rank p < 0.001 each). On multivariable analysis including age, Gleason grade group, tumour stage, ADT duration, docetaxel, and nodal radiotherapy, benefit of prostate radiotherapy persisted for bPFS [HR 0.33 (95% CI 0.18–0.62)], rPFS [HR 0.25 (0.12–0.51)], and OS [HR 0.27 (0.13–0.58)] (p < 0.001 each). Impact of nodal radiotherapy or docetaxel was not established due to small subgroups. Conclusion Addition of prostate radiotherapy to ADT in cN1M0 prostate cancer yielded improved disease control and overall survival independent of other tumour and treatment factors.