What is most apparent from the table are the higher rates of positive margins in obese men undergoing RALP. This is in line with the experience in open RP. One would expect, now, that experience with RALP has grown and that the increase in visualization and magnification could translate into a lower rate of positive margins.
And yet positive margin rates are nearly double in obese patients as compared with normal-weight individuals undergoing RALP. Whether these positive margins are biologic (associated with extracapsular extension [pT3a]) or iatrogenic (not associated with extracapsular extension [pT2]) is unknown.
If the majority of positive margins turns out to be pT2, then one would expect that the physical state and anatomic layout of obese patients precludes adequate surgical resection. Further analysis is warranted in this area, but with growing robotic experience in large volume centers, the positive margin rates between obese and non-obese individuals will likely become similar.
Surgical outcomes in the obese
Published data on functional outcomes related to obesity and prostate surgery are much scarcer than data on the impact of obesity on prostate cancer itself. Researchers at the University of California at Irvine report that obese patients had a slight delay in recovery as compared with nonobese men (Urology. 2005;65:740-744). In particular, BMI was found to be an independent predictor of return to continence at six months.
Additionally, urinary bother scores were significantly worse for obese patients. Results on erectile function were too premature to report in this analysis. At the University of Chicago, investigators observed no difference in return to continence for obese patients vs. nonobese patients. In fact, obese patients subjectively had the best continence rates until 12 month (Urology. 2006;67:774-779). The research group observed no difference in return of sexual function in obese patients as compared with nonobese men.
The largest reported analysis of the effect of an elevated BMI on RALP is from the Mayo Clinic (J Endourol. 2008;22:1471-1476). After following patients for a median 1.3 years, the group at Mayo reported that 93.8% of men in the obese cohort were continent at one year and no individuals required a secondary procedure for incontinence.
Again, there was no difference as compared with the nonobese group in this series. Of the patients in the Mayo analysis who had preoperative potency and for whom data were available, 69% of obese patients reported potency at one year as compared with 80.6% of normal weight individuals. It is worth noting that this analysis was performed with a non-validated institutional questionnaire. More mature data and further analysis in this area will help define the functional outcomes of obese patients undergoing RALP in the future.
One area that is quite interesting concerns the role obesity plays in treatment decisions of prostate cancer. In an analysis of the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) database undertaken during their previously described study, Davies et al looked at the odds ratio of receiving each type of prostate cancer treatment as compared with RALP according to BMI categories.
In this cohort of 5,041 men, approximately 21% met the criteria for obesity. The likelihood of a physician and/or patient choosing a nonsurgical form of treatment clearly increased as BMI increased. Whether this is the result of the obese patient’s opting for nonsurgical therapy or physician bias, more obese individuals are receiving nonsurgical therapy than their identically matched nonobese cohorts.
Data yet to come
The reported experiences of RALP as it relates to obesity are limited and suffer from several deficiencies. First, all the reported data are retrospective. There has never been a prospective, randomized study comparing obese vs. nonobese patients, and there has never been a comparison of open RP vs. RALP as the two relate to obesity. Second, most of the reported series are an early snapshot of each institution’s robotic experience.
Many, if not all, of the institutions listed in Table 1 now have a quite robust experience in RALP, and current perioperative parameters and functional outcomes may very well be different, since we know that the learning curve is important (Eur Urol. 2007;52:1090-1096; Eur Urol. 2006;49:866-872; and Urology 2007;70:96-100). Third, at this point, most of the functional outcomes following RALP as they relate to obesity are limited and lacking in the use of consistent, validated questionnaires.
Despite these drawbacks, I suspect that in the next year, emerging data will shed new light on the functional results of RALP in obese patients.
For patients with a BMI greater than 30 who are diagnosed with prostate cancer, numerous surgical treatments are now available. Practitioners can choose between open RP, RALP, laparoscopic prostatectomy, and perineal prostatectomy.
Thus far, there is insufficient evidence in the literature to support one form of surgical therapy over another, and the decision should rest with the experience of the individual surgeon. As experience with RALP grows, however, we will learn more about its potential advantages and disadvantages in men with prostate cancer who meet the WHO criteria of obesity.
Dr. Scherr is associate professor of urology and clinical director of urologic oncology at Weill Medical College of Cornell University in New York.
For more information about robotic prostatectomy, go to www.robotic-prostatectomy.com