A new study has found that obesity is associated with an increased risk for prostate cancer in African American men, a risk that grows by nearly four times as an individual’s body-mass index (BMI) increases.
It is known that African American men have the highest incidence of prostate cancer of any other racial or ethnic group in the United States as well as the highest rates of aggressive disease and prostate cancer death. While those risks likely arise from both social and biological factors, the associations of obesity with prostate cancer risk in this population are complex.
For this study, published online in JAMA Oncology, researchers analyzed data from 3398 African American men and 22,673 non-Hispanic white men participating in the SELECT [Selenium and Vitamin E Cancer Prevention] Trial, carried out between 2001-2011. During a median follow-up of 5.6 years, results showed that of the 1732 men that developed prostate cancer; 270 of them were African American whereas 1453 were non-Hispanic white males.
Obesity was not associated with the risk of prostate cancer overall among non-Hispanic white men; however, there was a significant association between obesity and the total risk for both low- and high-grade prostate cancer in African American men.
Results showed that being African American increased the risk for prostate cancer across BMI categories, jumping from 28% among African American men with a BMI less than 25 [normal and underweight] to 103% among African American men with a BMI of at least 35 [obese].
For low-grade prostate cancer, obesity was inversely associated with prostate cancer risk among non-Hispanic white men. Those with a BMI of at least 35 had a 20% reduced risk compared with non-Hispanic white men with a BMI of less than 25. However, the results showed that obesity was positively associated with the risk of high-grade prostate cancer among non-Hispanic white men.
While the reasons for these findings are unknown, the authors speculate that one explanation may be that the biological effects of obesity differ in African American and non-Hispanic white men.
“This study reinforces the importance of obesity prevention and treatment among African American men, for whom the health benefits may be comparatively large,” the authors concluded. “Although obesity is linked to poor health outcomes in all populations, clinicians might consider the unique contribution of obesity prevention and treatment to the health of their African American patients. Such targeted efforts may contribute to reductions in prostate cancer disparities.”
In an editor’s note, Charles R. Thomas Jr, MD, deputy editor of JAMA Oncology, noted, “Despite the limitations inherent in the methodology utilized for the analysis and the inability to define a clear mechanism behind the association between BMI and risk, the findings do provide a further rationale for weight reduction and a target BMI for clinicians to aim for in care of African American men.”