Adjuvant radiotherapy after salvage lymph node dissection because of nodal relapse of prostate cancer versus salvage lymph node dissection only

Background Nodal pelvic/retroperitoneal recurrent prostate cancer (PCa) after primary therapy can be treated with salvage lymph node dissection (salvage-LND) in order to delay disease progression and offer cure for a subset of patients. Whether adjuvant radiotherapy (ART) in affected regions improves the outcome by elimination of residual tumour burden remains unclear. Methods A total of 93 patients with exclusively nodal PCa relapse underwent choline-positron-emission tomography-computed-tomography-directed pelvic/retroperitoneal salvage-LND; 46 patients had surgery only and 47 patients received ART in regions with proven lymph node metastases. In case of subsequent prostate specific antigen (PSA) progression, different imaging modalities were performed to confirm next relapse within or outside the treated region (TR). Mean follow-up was 3.2 years. Results Lymphatic tumour burden was balanced between the two groups. Additional ART resulted in delayed relapse within TR (5-year relapse-free rate 70.7 %) versus surgery only (5-year relapse-free rate 26.3 %, p < 0.0001). In both treatment arms, time to next relapse outside the TR was almost equal (median 27 months versus 29.6 months, p = 0.359). With respect to the detection of the first new lesion, regardless if present within or outside the TR, 5 years after the treatment 34.3 % of patients in the group with additional ART were free of relapse, versus 15.4 % in the surgery only group (p = 0.0122). ART had no influence on the extent of PSA reduction at latest follow-up compared to treatment with surgery only. Conclusion ART after salvage-LND provides stable local control in TR and results in overall significant improved next-relapse-free survival, compared to patients who received surgery only in case of nodal PCa-relapse.