Robotic Prostatectomy and Obesity
Douglas S. Scherr, MD
During the past eight years, the use of robotic-assisted laparoscopic prostatectomy (RALP) for prostate cancer has grown tremendously and at a pace almost unparalleled in modern surgery.
Current estimates indicate that half of all prostatectomies done in the United States are done robotically, and that figure is likely to increase as more and more surgeons gain robotic experience. An abundance of reports in the literature tout the technical advantages of robotic surgery.
Many of those reports pertain to various technical aspects of robotic surgery as it applies to radical prostatectomy (RP). Now that most urologists have accepted some role of robotics in the surgical treatment of prostate cancer, it is important to get back to discussing many of the oncologic and disease-related aspects of this malignancy.
One area that has received considerable attention over the past few years is the impact of obesity on both robotic surgery and prostate cancer itself.
According to current estimates, more than 30% of the U.S. population is considered to be obese (BMI >30 kg/m2) and more than 70% of men over the age of 40 are obese or overweight. These numbers will likely continue to rise over the next several decades.
An aging U.S. population means that urologic practitioners will begin to see more and more patients with prostate cancer who meet World Health Organization (WHO) criteria for obesity.
Obesity's effect on prostate cancer
Reports regarding obesity and its impact on pathologic variables in prostate cancer abound. Although a true consensus has not been reached, it is generally agreed that obesity is a negative risk factor in prostate cancer. In particular, obesity has been found to be an independent factor associated with aggressive prostate cancer and risk of disease-related death (N Engl J Med. 2003;348:1625-1638).
Further, obesity is associated with higher Gleason score, an increased rate of positive surgical margins, and a higher progression rate in patients with a low likelihood of recurrence following therapy (e.g., J Clin Oncol. 2004;22:439-445; J Urol. 2005;174:919-922; and Urology. 2005;66:1060-1065).
In addition, while investigating the effect of BMI on primary treatment of cancer, Davies et al found that PSA screening is less effective in obese patients (Urology. 2008;72:406-411).
Not everyone is in agreement, however. A 10-year study at the Mayo Clinic followed more than 5,000 men who underwent RP. The researchers found that while a higher BMI was associated with worse pathologic features at the time of surgery, BMI was not an independent prognostic variable for biochemical recurrence or disease-free survival (Cancer. 2006;107:521-529).
Other investigators have shown that obesity is associated with higher pathologic grade and stage but not with biochemical failure after prostatectomy (Urology. 2008;72:1106-1110). There exists some evidence in Europe as well that an elevated BMI is not associated with worse clinicopathologic outcomes.
A recent study evaluated 1,538 consecutive patients treated by open RP; 11% had a BMI greater than 30 (Urology. 2008; published online ahead of print). Results showed that elevated BMI was unrelated to extracapsular disease, seminal-vesicle invasion, lymph-node metastases, or positive margin rate.
This raises the possibility of differences between obesity in Europe and obesity in the United States. Additionally, other factors not appreciated in Europe may be contributing to worse pathologic features in this country.
Impact of obesity on RALP
While we await further analyses regarding obesity and prostate cancer, including an investigation into specific dietary factors (e.g., saturated fats, soy intake, selenium, red wine, etc.), we must be prepared to manage the growing number of obese patients receiving this diagnosis.
Urologists will surely encounter obese patients and must be ready to counsel them and direct them toward appropriate treatment. Robotic surgery is obviously at the forefront of prostate cancer management, but most patient counseling today centers around anecdotal accounts and personal physician experience without any true understanding of the impact of an elevated BMI and RALP.
The table below depicts the international experience with RALP in obese individuals. The data clearly show that robotic prostatectomy can be accomplished in patients whose BMI is greater than 30 without any significant increase in morbidity compared with patients whose BMI is 25 or less. There is certainly a trend toward longer operative time, increased blood loss, and a higher complication rate with the higher BMI, although most differences are not statistically significant.
In addition, most of the reported experience in the table is from quite early in the process, as the institutions began to undertake RALP. With growing experience, the differences between obese and non-obese patients will become indistinguishable.