Interaction of obesity and race in predicting recurrence rates after radical prostatectomy

Abstract

5070 Background: Black men are twice as likely to die from prostate cancer compared to white men. Obese men are known to have higher mortality rates and recurrence rates, and blacks are 1.4 times as likely to be obese than white Americans. However, the relative contribution of BMI and race to biochemical failure (BCF) after radical prostatectomy (RP) has not been well-characterized. We examined the interaction of BMI and race in predicting BCF after RP. Methods: A retrospective analysis of the Columbia Urologic Oncology Database found that 3,736 consecutive men underwent RP between 1988 and 2008. 1,461 men had BMI and race data available. 213 (14.6%) were black men, 1,004 (68.7%) were white, 162 (11.1%) were Hispanic, and 82 (5.6%) were Asian. Overweight and obese men were defined as having a BMI > 25 kg/m2 and a BMI > 30 kg/m2, respectively. BCF was defined as a post-surgery PSA level >0.2 ng/mL on > 2 measurements. Cox regression methods were used to model the relationship between race, BMI and BCF. Results: The 1,461 men had a median age of 60 years, and median pre-operative PSA of 5.5. There was no significant difference in BMI among the four races (p = 0.58). The 5 year disease-free survival for black obese men was the lowest at 69%, compared to non-obese black (71%), obese white (80%), and non-obese white men (80%, p < 0.001). BMI did not have a significant impact on BCF. After adjusting for preoperative PSA level, tumor stage, and Gleason sum, race remained an independent predictor of BCF (HR = 1.65, p = 0.04). An analysis assessing the effect of an interaction between race and BMI demonstrated that hazard ratios for increased BMI did not differ significantly by race. Black men who were normal, overweight and obese were 2.0, 3.0 and 2.5 times more likely than white men to have BCF in the respective weight categories, but the differences were not significant. Conclusions: Black race is an independent predictor of biochemical failure after adjusting for pathologic factors. The impact of BMI on BCF did not vary among different races. However, BMI does contribute to the accurate estimation of the risk of BCF. These findings suggest that elevated BMI does not affect the BCF rates of black men more than in other races, and that other factors may influence the racial variability in disease-free survival and BCF risk. No significant financial relationships to disclose.