PSMA-PET/CT-based salvage elective nodal radiotherapy for lymph node recurrence following radical prostatectomy.

Purpose: For patients with oligometastatic nodal recurrence after radical prostatectomy (RP), salvage radiotherapy is a valuable curative second-line treatment option. However, few clinical data on the impact of PSMA-PET/CT-based salvage elective nodal radiotherapy (sENRT) is available. In order to contribute further clinical data on the outcome of patients treated with sENRT following RP, we analysed the rates of biochemical recurrence-free survival (BRFS) and distant metastasis-free survival (DMFS) as well as potential predictive markers for optimised patient selection.

Methods: A retrospective analysis of 76 patients treated with sENRT for nodal recurrence after RP was performed. Primary endpoints were BRFS and DMFS. Cox proportional hazards model was used to analyse potential predictive factors.

Results: Median follow-up was 32.6 months. PSMA-PET/CT revealed 1, 2, or ≥ 3 positive lymph nodes in 63.2%, 30.2% and 6.6% of patients, respectively. 96% of the patients had pelvic-only lymph nodes involvement. One-, two- and three-year BRFS were 98.6%, 84.2%, and 71.9%, respectively. Notably, nodal status at the time of RP and biochemical-recurrence prior to sENRT, were associated with reduced BRFS. One-, two-, and three-year DMFS were 98.7%, 94.1%, and 94.1%, respectively, with paraaortic lymph nodes being the only factor indicating reduced DMFS. Concomitant androgen-deprivation therapy was applied in 85.5% of the patients.

Conclusion: We present one of the largest studies on PSMA-PET-based sENRT for nodal recurrence after RP with promising results, highlighting the important role of sENRT. Regarding patient selection, initial lymph node status and prior radiation of the prostate were predictive of reduced BRFS, while involvement of paraaortic lymph nodes was identified as marker for reduced DMFS.