The impact of body mass index on treatment recommendations for patients with intermediate risk prostate cancer.

Abstract

48 Background: To evaluate the clinical utility of body mass index (BMI) in predicting adverse pathologic outcomes, hence the need for radiation therapy (RT) following radical prostatectomy (RP) for men with organ-confined prostate cancer. Methods: We compared BMI and preoperative risk factors to adverse pathologic risk factors (RP-risk) that dictate the use of RT following RP. Multivariate analysis was used to determine whether BMI provides clinically relevant information in predicting RP-risk for additional RT as well as biochemical outcome. Results: Patients with elevated BMI had higher RP-risk (p=0.002). Specifically, extraprostatic extension, p less than 0.001; positive surgical margins, p=0.005; and a trend towards worse seminal vesicle invasion, p=0.08. Elevated BMI did not correlate with preoperative risk groupings (p=0.38). However, in patients with intermediate-risk disease BMI greater than 29kg/m2 was strongly associated with higher RP-risk (p=0.03) and higher rate of pathologic upgrading of tumors (p<0.004). Intermediate risk patients with BMI greater than 29kg/m2had a two-fold increased risk of requiring RT following RP based on greater than or equal to two adverse pathologic factors (15% vs. 34%). After controlling for known preoperative risk factors, BMI was an independent predictor of RP-risk for additional RT (p=0.006) and biochemical recurrence (p=0.03). Conclusions: BMI of greater than 29kg/m2 is an independent predictor of adverse RP-risk requiring additional RT, particularly in patients with intermediate risk disease. This select group of patients may be best treated with definitive radiation therapy to prevent the additional toxicity from adjuvant or salvage RT following RP. We propose including BMI in clinical decision-making for appropriate treatment recommendation for patients with intermediate risk prostate cancer.