39 Background: It is important to determine whether changes in technology have impacted surgical practice. With the adoption of robotic surgery, it is our hypothesis that rates of pelvic lymphadenectomy (LND) have decreased, even when controlling for cancer risk and comorbidities. To assess whether adoption of surgical technology versus practice patterns in the extent of surgery over time changed, we propose to compare the rates of pelvic LND at the time of radical prostatectomy during the time period when robotic surgery was adopted. Methods: Data was extracted from CaPSURE, a multi-institutional, longitudinal observational database of men with prostate cancer. A total of 3,938 men diagnosed with localized prostate cancer between 2000 and 2011 were included in the analysis if they underwent surgical extirpation. The inclusion of LND was calculated for both groups. Other information included site type, age at diagnosis, comorbidities, and CAPRA risk assessment score. Results: A total of 3,616 open retropubic prostatectomies and 322 robotic prostatectomies were included for analysis. Among the open prostatectomies, 78.9% underwent pelvic LND. During the same time period, among robotic prostatectomies, 45.3% underwent pelvic LND. There was a statistically significant correlation between method of radical prostatectomy and the performance of LND (p < 0.001). There were no statistically significant differences between the two groups in CAPRA score, age, or comorbidities (p= 0.06, 0.29, and 0.60; respectively). The adjusted odds ratio of LND for the open group compared to the robotic group is 5.90 (95% CI [4.48,7.78]) while adjusting for clinical stage, grade, and PSA. Conclusions: Controlling for other factors, the difference in rates of LND between the open and robotic groups were statistically significant. These data suggest changes in surgical practice may have been altered by the adoption of a new technique to perform surgery (rather than new scientific data supporting omission of LND).