Objectives

To evaluate the association between obesity and positive surgical margins in patients undergoing retropubic radical prostatectomy versus robotic-assisted laparoscopic prostatectomy.

Methods

We retrospectively reviewed the data of 3141 men undergoing retropubic radical prostatectomy and 1625 undergoing robotic-assisted laparoscopic prostatectomy between 1988 and 2017 at eight Veterans Health Administration hospitals. The positive surgical margin location (peripheral, apical, bladder neck, overall) was determined from pathology reports. We adjusted for age, race, prostate-specific antigen, surgery year, prostate weight, pathological grade group, extracapsular extension, seminal vesicle invasion, hospital surgical volume and surgical method (in analyses not stratified by surgical method). Interactions between body mass index and surgical approach were tested.

Results

Among all patients, higher body mass index was associated with increased odds of overall, peripheral and apical positive surgical margins (OR 1.02-1.03, P ≤ 0.02). Although not statistically significant, there was a trend between higher body mass index and increased odds of bladder neck positive surgical margins (OR 1.03, P = 0.09). Interactions between body mass index and surgical method were significant for peripheral positive surgical margins only (P = 0.024). Specifically, there was an association between body mass index and peripheral positive surgical margins among men undergoing retropubic radical prostatectomy (OR 1.04, P < 0.001), but not robotic-assisted laparoscopic prostatectomy (OR 1.00, P = 0.98). Limitations include lacking individual surgeon data and lacking central pathology review.

Conclusions

In this multicenter cohort, higher body mass index was associated with increased odds of positive surgical margins at all locations except the bladder neck. Furthermore, there was a significant association between obesity and peripheral positive surgical margins in men undergoing retropubic radical prostatectomy, but not robotic-assisted laparoscopic prostatectomy. Long-term clinical significance requires further study.