Efficacy of local treatment in patients with prostate cancer with clinically pelvic lymph node-positive disease at initial diagnosis.

164 Background: There is limited evidence supporting the use of local treatment (LT) for prostate cancer (PCa) patients with clinically pelvic lymph node-positive (cN1) disease. Against this backdrop, we sought to examine the efficacy of any form of LT+/-androgen deprivation therapy (ADT) in treating these individuals. Methods: Within the National Cancer Data Base (2004-2012), we identified 2,967 individuals who received LT+/-ADT vs. ADT alone for cN1 PCa. Only radical prostatectomy (RP) and radiation therapy (RT) were considered as definitive LT. Instrumental variable analyses (IVA) were performed using a two-stage residual inclusion approach to compare overall mortality-free survival between patients who were treated with LT+/-ADT vs. ADT alone. The same methodology was used to further compare overall mortality-free survival between patients who were treated with RP+/-ADT vs. RT+/-ADT. Results: Overall, 1,987 (67.0%) and 980 (33.0%) patients received LT+/-ADT and ADT alone, respectively. In the LT+/-ADT group, 751 (37.8%) and 1,236 (62.2%) patients received RP+/-ADT and RT+/-ADT, respectively. In IVA, LT+/-ADT was associated with a significant overall mortality-free survival benefit (HR = 0.31; 95% CI = [0.13-0.74]; P= 0.007), when compared to ADT alone. At 5-year, overall mortality-free survival was 78.8% (95% CI: 74.1%-83.9%) vs. 49.2% (95% CI: 33.9%-71.4%) in the LT+/-ADT vs. ADT alone groups. When comparing RP+/-ADT vs. RT+/-ADT, IVA showed no significant difference in survival between the two treatment modalities (HR = 0.54; 95% CI = [0.19-1.52]; P= 0.24). Conclusions: Our study shows a significant overall mortality-free survival benefit for cN1 PCa patients who were treated with LT+/-ADT as compared to their counterparts treated with ADT alone. Conversely, no significant survival difference was observed between patients treated with RP+/-ADT vs. RT+/-ADT.