Abstract
I
As stated by the authors, obesity is a modifiable lifestyle factor and risk for several end points of cancer outcomes. Recently, obesity has been shown as a statistically significant predictor of conversion to open prostatectomy, 1 intraprostatic incision into malignant glands, 2 biochemical failure, 3,4 and overall survival. 4 The risk predates the operation because obesity also predicts for high-grade cancer at biopsy but not overall positive biopsy rate. 5
What can we conclude about the causality between obesity and outcomes? As proposed by the authors, access to the prostate may be obstructed when you combine the more difficult port placement, distance the instruments must reach, and issues with hemostasis. Indeed, I have long observed that adipose tissue inhibits mono- and bipolar current coagulation and produces more smoke in the field compared with leaner patients.
The ultimate goal for the surgeon is to achieve optimal exposure to the key angles to the prostate—anterior, bladder neck, posterior-lateral, perirectal, and apex—and this allows the critical steps of bladder neck division, seminal vesicle dissection, nerve bundle sparing, and apical division. Any features that combine to “steal space” around the prostate may make the dissection more difficult and affect the perioperative, oncologic, and functional outcomes.
Indeed the “perfect storm” of RARP complexity is the combination of obesity, large gland size, and pubic arch interference—the latter most impressive when the entire gland sits under the pubic arch. Of interest, however, is that most experienced RARP surgeons who previously were trained and experienced in open surgery will still prefer to approach these patients robotically and use various manipulations of the port placements, port angles (i.e., “burping” the port up to create more space between instruments or down to allow the instrument to clear under the pubic bone).
As the authors suggest, surgeons in their learning curve may be advised to be selective with obesity early on, and a specific example would be the anastomosis where with obese patients and pubic arch interference, the surgeon will have to use a number of clever suturing angles to pass the needle in and out of the urethra. Beyond these access issues, however, there are several interesting biologic causes proposed for the linkage between obesity and genitourinary cancers. 6
Finally, there is another key question with obesity that is generally not an easy to publish end point and not present in this meta-analysis: What is the upper end point of BMI that is safe for RARP? This is mostly an empiric point of observation and trial and error. The potential rate limiting aspects are the upper limits of ventilating a patient in the steep Trendelenburg (generally 30–40 degrees head down) position, and the risk of positioning injuries.
Personally, I have not had issues with patients up to a BMI of 40, and beyond this point, the risk of poor ventilation and retained C02 start to increase. Therefore, I generally work on weight loss with patients in the BMI 40 to 50, unless their weight distribution is not so centralized in the abdomen (i.e., large limbs). There remains a significant management challenge for patients with BMIs in excess of 50, such that the concept of bariatric surgery has been considered.