April 16, 2015
3 min read

Obesity increases prostate cancer risk in black men

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Obesity was significantly associated with the overall risk for prostate cancer in black men but not in non-Hispanic white men, according to results of a prospective study.

The risk for prostate cancer among black men increased by nearly four times as their BMI increased, results showed.

Black men have the highest incidence of prostate cancer, the highest rate of aggressive disease and the highest rate of prostate cancer-related death of any racial or ethnic group in the United States, which is likely associated with social and biologic factors, according to study background.

Wendy E. Barrington, PhD, an assistant professor in the department of psychosocial and community health at the University of Washington School of Nursing, and colleagues sought to evaluate the association between obesity with prostate cancer risk due to results from previous studies that found obesity was associated with an increased risk for low- and high-grade prostate cancer among U.S. and Caribbean black men.

The current analysis included 3,398 black men and 22,673 non-Hispanic white men who had participated in the SELECT trial between 2001 and 2011.

During a median follow-up of 5.6 years, 1,723 men developed prostate cancer. Of these men, 270 were black, 148 of whom had low-grade cancer and 88 of whom had high-grade cancer. The other 1,453 cases of cancer occurred in non-Hispanic white men, 898 of which were low-grade cancer and 441 of which were high-grade cancer.

Overall, black men experienced a 58% increased risk for prostate cancer compared with non-Hispanic white men (OR = 1.58; 95% CI, 1.37-1.81).

There was no association between BMI and risk for prostate cancer among non-Hispanic white men; however, BMI was positively associated with risk among black men. When comparing a BMI of less than 25 kg/m2 with a BMI of at least 35 kg/m2 among black men, the HR for prostate cancer was 1.49 (95% CI, 0.95-2.34).

The risk for prostate cancer among black men increased from 28% (HR = 1.28; 95% CI, 0.91-1.8) for those with a BMI less than 25 kg/m2 to 103% (HR = 2.03; 95% CI, 1.38-2.98) among those with a BMI of at least 35 kg/m2.

BMI had an inverse association with low-grade prostate cancer risk for non-Hispanic white men (BMI ˂ 25 kg/m2 vs. ≥ 35 kg/m2; HR = 0.8; 95% CI, 0.58-1.09). However, this association was positive among black men (HR = 2.22; 95% CI, 1.17-4.21).

BMI was associated with a greater risk for high-grade prostate cancer in non-Hispanic white men (HR = 1.33; 95% CI, 0.9-1.97) and black men (HR = 1.81; 95% CI, 0.79-4.11); however, the racial interaction did not differ significantly across obesity categories.

The researchers wrote that the biological effects of obesity may differ between black and non-Hispanic white men.

“Inflammation plays a role in prostate carcinogenesis, and the effect of obesity on systemic inflammation could be stronger in African American than non-Hispanic white men,” Barrington and colleagues wrote. “There are also known prostate cancer risk alleles that are more prevalent among African American men with which obesity may interact and modify their function.”

The researchers also suggested that detection of prostate cancer, despite screening recommendations based on site-based standard of care, may still be higher in the black men who participated in SELECT than the non-Hispanic white men in the trial.

Researchers identified study limitations that included BMI being a nonspecific measure of obesity, a possible racial difference in the proportion of men who elected a biopsy after an elevated screening result, and that the men in the study were from a clinic-based sample and may not be completely indicative of the general population.

“This study reinforces the importance of obesity prevention and treatment among African American men, for whom the health benefits may be comparatively large,” Barrington and colleagues wrote. “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.”

These findings should help provide a rationale for weight loss in the susceptible population, Charles R. Thomas Jr., MD, a professor and chair of the department of radiation medicine at Oregon Health and Science University, wrote in an invited commentary.

“If risk factors for the development of prostate cancer can be identified, it is possible that primary care practitioners may be able to focus on risk-reduction strategies,” Thomas wrote. “To this end, [this] study… presents results via joint-effects modeling to describe the effect of an interaction between race and obesity on risk of prostate cancer. … 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.” – by Anthony SanFilippo

Disclosure: The researchers and Thomas report no relevant financial disclosures.