Obesity Linked to Prostate Cancer in Black Men

A study by researchers in Seattle and their colleagues has found that obesity is linked to a significantly increased risk of prostate cancer in black men. This includes both low-grade (slow-growing) and high-grade (fast-growing) cancers. But among white men, the link between obesity and prostate cancer was less clear-cut. The study was published online April 16, 2015 in JAMA Oncology.

Black men have the highest rates of prostate cancer cases and the highest rates of prostate cancer deaths in the US. Understanding the reasons behind these disparities could help influence behaviors that may help lower the risks.

For the study, the researchers looked at the data of 3,398 black men and 22,673 white men who had taken part in the SELECT trial. The SELECT trial began in 2001 to find out whether selenium and vitamin E supplements could help prevent prostate cancer. The study was stopped early because analysis suggested the supplements did not work, and could actually be harmful. Men in the SELECT trial gave weight-related information that the Seattle researchers used for this new study.

During a follow-up period of about 5 ½ years, 270 black men and 1,453 white men in the study developed prostate cancer. Overall, the study found a 58% increased risk for prostate cancer among black men compared with white men. And obese black men were found to have an even greater increase in risk.

Very obese black men, those with a body mass index (BMI) of 35 or greater, were more likely to develop prostate cancer than those with a BMI below 25, which is considered to represent a healthy weight. Black men with a BMI below 25 had a 28% increased prostate cancer risk compared to white men in the same weight group; black men with a BMI of at least 35 had a 103% increased prostate cancer risk compared to white men in the same weight group.

Obesity among black men was linked to greater risk of both low-grade and high-grade prostate cancer. In white men the relationship was more complex: obesity was linked with a lower risk of low-grade cancer but a higher risk of high-grade cancer. The researchers defined low-grade prostate cancer as a Gleason score below 7 and high-grade prostate cancer as a Gleason score of 7 or above. A Gleason score is reached by looking at a sample of prostate cancer cells and comparing it to normal prostate cells. The higher the score, the more different the cells in the cancerous tissue look from normal prostate tissue.

More study is needed

The researchers point out that the links between obesity and prostate cancer are complicated, and the increased risks in black men likely stem from social as well as biological factors. More study is needed to find out whether weight loss in men who are obese would actually reduce their prostate cancer risk.

According to Durado Brooks, MD, MPH, American Cancer Society Director, Cancer Control Intervention, "It is important to recognize that obesity is influenced by a variety of factors, including genetic factors and environmental exposures. Therefore the results of this study may reflect the impact of other factors as opposed to a causal relationship between obesity and prostate cancer. Hopefully further studies of this association will elucidate the nature of this link."

Being overweight or obese is known to to be linked to a higher risk of some other cancer types, including colon, esophagus, kidney, and pancreatic cancer. It also raises the risk for heart disease and diabetes. The American Cancer Society recommends eating right and getting enough physical activity to help get to and stay at a healthy weight. For those who are overweight or obese, losing even a small amount of weight has health benefits and is a good place to start.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Difference in Association of Obesity With Prostate Cancer Risk Between US African American and Non-Hispanic White Men in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Published online April 16, 2015 in JAMA Oncology. First author Wendy E. Barrington, PhD, University of Washington, Seattle.

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