Prostate cancer is the second most commonly diagnosed cancer in men worldwide, apart from non-melanoma skin cancer. Radical prostatectomy (RP) provides durable, effective control of prostate cancer and results in high survival rates. However, many men experience long-term complications that can have an adverse impact on their quality of life, the most common and distressing of which are urinary incontinence and sexual dysfunction. 

Efforts to improve urinary incontinence and sexual dysfunction often focus on surgical and pharmacologic interventions, but non-surgical techniques, such as pelvic floor (i.e., Kegel) exercises and biofeedback techniques aimed at improving muscle tone, are also used. Emerging evidence also suggests that other aspects of physical health, such as body size, may be related to post-prostatectomy urinary and sexual function. However, the utility of this evidence is limited by several methodologic concerns including small sample sizes, crude measures, and lack of pre-surgical assessments. Therefore, to address these limitations and add to the limited literature on this topic, we prospectively examined the influence of obesity on urinary and sexual outcomes in men with clinically localized prostate cancer treated by radical prostatectomy in the Prostatectomy, Incontinence and Erectile function (PIE) study.

Study participants were recruited from 2011 to 2014 at two US institutions. At the pre-surgical baseline, participants provided self-reported information on urinary and sexual outcomes using the modified Expanded Prostate Cancer Index Composite (EPIC, scale from 0-100) and had their weight and height measured. Urinary and sexual function data were collected 5 weeks, 6 months, and 12 months after surgery and compared to baseline values using linear generalized estimating equations (GEE). Logistic GEE models were used to evaluate the likelihood of recovering urinary and sexual function (to within less than the minimal clinically meaningful difference from baseline) at 6 and 12 months.

Of the 407 eligible participants, 68.6% did not have obesity at baseline. Prior to surgery, men without obesity had similar levels of urinary function (p=0.151) as men with obesity, but higher levels of sexual function (p=0.005). Following surgery, urinary and sexual function scores declined dramatically in most men at 5 weeks but recovered to baseline levels in approximately 50% of participants for urinary function and 30% for sexual function at 12 months. However, urinary and sexual function levels were not uniform to obesity post-prostatectomy. Men without obesity at baseline had higher urinary function (p<0.001) at 6 months post-RP than those with obesity. This pattern of findings persisted at 12 months (p=0.008). In the multivariable logistic regression models, men without obesity at baseline were more likely to recover their urinary function (OR=2.50, 95% CI: 1.37-6.23) at 6 months than men with obesity (Table 2). However, this association attenuated to non-significant or null estimates by 12 months post-RP, suggesting more rapid recovery of incontinence for men without than with obesity. For sexual function, men without obesity at baseline had higher levels of sexual function at 6 months (p=0.028) and 12 months (p=0.051) in the multivariate-adjusted linear GEE models. Nevertheless, logistic GEE models found no associations between pre-surgical BMI and recovery of sexual function, suggesting that similar proportions of men recovered their sexual function post-RP.

In our large prospective study of prostate cancer survivors treated by RP, approximately 50% and 30% of participants achieved clinically meaningful recovery in urinary and sexual outcomes, respectively, over one year. Not having obesity at baseline before surgery was associated with better sexual, but not urinary outcomes. Shortly after surgery, all men experienced sharp declines in urinary and sexual function scores, but urinary function recovered faster and to more satisfactory values in men without than with obesity. For sexual outcomes, the likelihood of recovery was similar by obesity, but because men without obesity started at higher levels than men with obesity, they also returned to higher levels post-RP. 

The detrimental effect of pre-surgical obesity on urinary and sexual function post-RP opens up opportunities for future pre-surgical weight-loss interventions. These types of interventions would not need to be lengthy because body fat, particularly visceral fat, is very sensitive to behavioral weight-loss interventions, such as exercise and dietary modification. Given that the average waiting time between diagnosis and surgical treatment is approximately one month, this waiting period provides an ideal opportunity to implement a brief weight loss intervention. It could also open a dialogue between clinicians and patients about the myriad other benefits of maintaining a healthy weight, such as reducing their risk of later prostate cancer recurrence and mortality. 
Besides the potential for lifestyle counseling, our findings could also be used to counsel patients about their likely function and recovery after prostatectomy according to their health status. Better mental preparation about the side effects of surgery before RP could lead to greater psychological well-being after surgery, including greater satisfaction with their surgery, and less side effect-related distress and bother. Thus, our obesity-related findings could also be incorporated into future interventions aimed at better preparing patients for the side effects of surgery or helping men or couples adapt to the loss of function.

Prostate cancer survivors without obesity before surgery had better and likely earlier recovery in urinary function. Prostate cancer survivors without pre-surgical obesity also had better sexual functions at baseline, which persisted during post-surgical recovery.