Objectives: To evaluate patterns of practice and outcome of pelvic lymph node irradiation (PLNRT) vs. prostate bed irradiation (PBRT) in conjunction with androgen deprivation therapy after a radical prostatectomy (RP) in the context of adjuvant (ART) and salvage RT (SRT).
Methods: BC Cancer registry data (1995 – 2015) was used to identify 3450 patients who underwent RP and subsequently were referred to a cancer centre. Of those, 2370 received curative intent radiotherapy (RT). Patients were grouped according to their T stage and Gleason score into 4 risk groups: Low risk (T≤2 and GS≤7; n= 124), intermediate risk group A (T≥3 and GS≤7; n= 453), intermediate risk group B (T≤2 and GS≥8; n= 29) and high risk (T≥3 and GS≥8; n= 264). clinical, pathological and treatment characteristics were reviewed and analysed for overall survival (OS) correlating with administration of PLNRT and PBRT in each group using univariate analysis.
Results: The addition of PLNRT did not confer any OS benefit for the intermediate and high-risk group. OS in the low risk group who received PBRT was superior to PLNRT (p=0.0074). OS benefit was however only maintained for patients who also received ADT (p=0.01). The administration of ADT did not alter OS in any of the other groups. In the high-risk group, subset analysis revealed PLNRT to be superior to PBRT when there was confirmed pathological lymph node involvement (p=0.0082). Radiotherapy timing or type (adjuvant or salvage) did not contribute to any differences in OS in any of the groups. Although, when comparing ART and SRT in the presence of ADT, ART had superior OS to SRT but only in the low risk group.
Conclusion: After a RP, addition of PLNRT conferred survival benefit compared with PBRT for high-risk patients with lymph node involvement, regardless of whether the intent was ART or SRT. On preliminary analysis PLNRT was not superior to PBRT in the low risk group supporting the use of PLNRT only in individuals with higher risk disease. Future directions include multivariate analysis including margin status and biochemical failure as well as comparing observation vs RT in this cohort.
