Outcomes following external beam radiotherapy to the prostate and pelvic lymph nodes in addition to androgen deprivation therapy in non-metastatic prostate adenocarcinoma with regional lymph node involvement: a retrospective cohort study

OBJECTIVE: There is a paucity of evidence for external beam radiotherapy (EBRT) in patients with non-metastatic prostate adenocarcinoma with regional lymph nodes (cN1) as primary treatment in addition to androgen deprivation therapy (ADT). We present the retrospective outcomes of cN1 patients treated with prostate and pelvic nodal (PPLN) EBRT and ADT. METHODS: The clinical records of cN1 patients given PPLN EBRT from January 2012 to January 2020 were retrospectively reviewed. Primary outcomes of overall survival, prostate cancer-specific survival, and failure-free survival were analysed. Secondary outcomes of biochemical relapse-free survival, locoregional recurrence-free survival, and distant metastases-free survival were also reviewed. The prognostic values of clinicopathological parameters were investigated. Treatment toxicity was also reviewed. RESULTS: We identified 121 cN1 patients treated with PPLN EBRT and ADT. Treatment was well tolerated, with only a minority (1.7%) having Grade 3 toxicities. 5-year overall survival and prostate cancer-specific survival were 74.4 and 89.1% respectively. 5-year failure-free survival was 55.4%; with 5-year biochemical relapse-free survival, locoregional recurrence-free survival, and distant metastases-free survival at 56.2%, 85.2%, and 65.4% respectively. The benefits of PPLN EBRT were seen in most patients, with prolonged failure-free period and good loco-regional control. CONCLUSION: Patients with cN1 disease should be considered for PPLN EBRT, in addition to ADT. Treatment is well tolerated with low toxicity, good locoregional control, and prolonged time to disease progression. ADVANCES IN KNOWLEDGE: We report real-world experience of cN1 patients treated with PPLN EBRT in addition to ADT, with good outcomes following treatment and low toxicity.