Long Term Results of Elective Nodal Salvage Radiotherapy in Oligometastatic Prostate Cancer : A Mono-Institutional Series

Background The development of new metabolic diagnostic imaging PET is changing the history of metastatic prostate cancer (pCa), identifying situations of progression with a low disease burden; radiation treatment of metabolically active oligometastatic sites has been shown to be effective to prolong patient survival. In the scenario of oligometastatic disease to pelvic lymph nodes there is no uniform consensus on treatment volumes and radiotherapy doses to use. Methods We retrospectively assessed a series of 50 patients treated from 2015 to 2021 at our center who presented with recurrent pelvic lymph node pCa disease with 1-3 lymph-nodes lateralized to one side of the pelvis. Patients were treated with intensity modulated Rapid Arc radiotherapy (IMRT), limiting the treatment volume to the chain of the affected side only. During the follow-up, the patients who presented a biochemical recurrence of the disease were evaluated by PET. Results The biochemical progression-free survival and the metastatic progression-free survival were respectively 36% and 49% at 5 years. 22/50 patients presented a documented recurrence on PET. Only one patient presented a relapse within the irradiated volume and no patient presented a relapse on the contralateral pelvic lymph node chain. No patient had gastrointestinal toxicity > grade 1 RTOG. Conclusion Treatment of patients with oligorecurrent (1-3 lesions) pelvic pCa, limiting the volume of irradiation to only one side of the affected lymph node chain, results in good biochemical disease control and presents a low risk of neoplastic contralateral progression.