Obesity is one of the most pressing issues facing the US healthcare system. Beyond its known associations with diabetes, coronary artery disease, and hypertension, obesity also has a significant impact on mortality in cancer patients.2
With over 70% of US men over age 40 over-weight and obese, urologists will have to deal with the ramifications of this epidemic.1
In particular, prostate cancer is one disease in which elevated BMI likely plays a significant role. Although there have been some conflicting studies, obesity appears to correlate with higher grade and more aggressive disease, as well as an increased likelihood of death from prostate cancer.2,4,13–17
Elevated BMI has been associated with biochemical failure after radical prostatectomy. Whether this is due to aggressive disease biology or to technical limitations is not fully clear. Freedland and colleagues7
attempted to determine whether the increased rate of biochemical failure in obese patients was due to technically inferior surgery. Using capsular incision on the pathological specimen as a proxy for a worse technical operation, they found that mildly obese patients had a 30% increased chance of capsular incision and moderately to severely obese men had a 57% increased risk. Several other studies have further noted a trend towards increased positive surgical margins in the overweight and obese patients.4,5
Interestingly, however, in a study of postprostatectomy patients with negative surgical margins, the SEARCH database study group still found an increased risk of biochemical failure in patients with elevated BMI.14
This observation led to the conclusion that a technically inferior operation cannot fully account for the outcome differences.
Robotic radical prostatectomy has been shown to be a reasonable and effective treatment modality for prostate cancer.8–10
However, the impact of BMI on the effectiveness of this surgical procedure has yet to be fully elucidated. To date, there are only 2 studies that have investigated surgical outcomes of robotic prostatectomy in overweight and obese men compared with men with normal BMI.11,12
We add to this literature by contributing our experience with a large series of patients from a single academic institution. Similar to the 2 prior studies, we failed to note any statistical difference in age, baseline PSA, clinical T stage, or biopsy Gleason score among our cohorts. Of note, the disease characteristics of patients in all of these studies may reflect a selection bias towards men who are surgically fit for an operative procedure. We acknowledge that our study, as well as others, may therefore be selecting the “healthiest” of the heavy patients. Our series demonstrated that obese men had a significantly longer operative duration (by almost 60 minutes) compared with overweight and normal BMI men. It is likely that this prolonged operative time is at least partly related to the increased blood loss seen in obese men in all 3 studies. Other factors that may contribute to this increased surgical time include suboptimal port placement, robotic arm positioning, dissection of fat planes, and closure.
In addition to the prolonged operative time and increased blood loss, trends towards decreased bilateral nerve sparing, increased open conversions, and longer hospitalization in overweight and obese patients all point to a technically more challenging operation. Despite this, there was no difference in complication rates between the cohorts suggesting that even with a technically more challenging operation, overweight and obese patients were not at increased risk from the surgery itself.
Beyond the perioperative variables discussed above, oncologic control is of paramount importance. Our data noted no difference in biochemical recurrence rates between the 3 groups at relatively short 1-year follow-up. Although the ultimate measure of an intervention is the ability to prolong long-term survival, surgical technique can be assessed in the short-term by analyzing pertinent oncological variables such as pathologic margin status. It is generally agreed that a positive margin is indicative of incomplete tumor resection and bears significant prognostic importance. Several institutions have demonstrated the independent prognostic significance of positive surgical margins across all stages of disease.18
In our series, there was a trend towards increased positive surgical margins between normal (11%), overweight (20%), and obese (21%) men. While this could reflect the inherent technical difficulties of operating on heavy patients, it may also be due to the advanced disease noted among men with elevated BMI. Indeed, in our series, the obese and over-weight patients had an increased incidence of pT3 cancers than did normal BMI men (15% and 18% vs 8%, respectively). This increase in locally advanced disease, though not significant, further confirms observations in the literature that these men are at increased risk of aggressive cancer. Future studies with larger cohorts of patients that control for pathologic stage will be needed to explore the causative factor behind the increased positive surgical margin rates.
Finally, postoperative quality of life is an important consideration when counseling patients. Our preliminary data (not shown) suggests that potency and continence rates are similar among the study groups. Interestingly, we did note a trend towards better bilateral nerve sparing in patients in the normal BMI group. This may eventually translate into better erectile function, though longer-term data are needed. Clearly, both issues require further investigation with patient-based validated questionnaires, and we are waiting for our data to mature before commenting more definitively. Indeed, spontaneous improvements in continence and potency continue up to 2 years following radical prostatectomy, thus emphasizing the evolving nature of these variables.19,20