Introduction

Salvage radiation therapy (SRT) is a therapeutic option for men with PSA rising after radical prostatectomy (RP). While several studies have addressed potential predictors of outcome after SRT, none have investigated the role of the extent of pelvic lymph node dissection (PLND) on SRT outcomes. We hypothesised that cancer control of SRT are improved in men who underwent more extensive PLND at the time of RP.

Methods

The study included 728 patients who received SRT for either PSA rising after RP or PSA persistence after surgery that was defined as PSA level ≥0.1 ng/ml 1 month after RP. All patients received local radiation to the prostate and seminal vesicle bed at one of six tertiary referral centres; irradiation of the pelvic lymph node region (whole pelvic RT) was left to the discretion of the treating physician. The study outcome consisted of clinical recurrence after SRT as identified by radiologic imaging. Clinical recurrence included pelvic nodal, retroperitoneal nodal, skeletal, and visceral metastasis. Multivariable analysis tested the association between clinical recurrence and the number of lymph nodes removed, which was considered as a continuous variable. Covariates consisted of: pT stage (≤pT3a vs. ≥pT3b), pathologic Gleason score (≤7 vs. ≥8), surgical margin (negative vs. positive), PSA level at SRT, and radiation field (prostatic bed vs. whole pelvis).

Results

Median patient age was 66 years, while the median number of nodes removed at RP was 7 (IQR 0, 13). Overall, 500 (69%) patients received SRT for PSA rising after RP and 228 (31%) were irradiated for PSA persistence. Median PSA at SRT was 0.30 ng/ml. Whole pelvic SRT was delivered to 187 (27%) patients. Median follow-up was 94 months (IQR 48, 128), during which time. 27 (3.7%), 13 (2.1%), 61 (7.7%), and 11 (1.3%) patients developed pelvic, retroperitoneal, skeletal, and visceral metastasis, respectively. On multivariable analysis, the number of lymph nodes removed at RP was significantly inversely associated with the risk of clinical recurrence following SRT (hazard ratio: 0.97; 95% CI 0.95, 0.99; p=0.039).

Conclusions

This is the first study demonstrating a significant inverse correlation between the number of lymph nodes removed and the risk of clinical recurrence after SRT. These data suggest the need for consideration of alternative approaches to management for patients with PSA elevation after RP in whom a lower number of nodes were removed at surgery, including multimodal salvage therapy.

Funding

none