Researchers suggest that such disorders may lower PSA levels, delaying biopsies.

Obesity and diabetes might mask the onset of prostate cancer in African-American and Caucasian men, respectively, according to researchers at Vanderbilt-Ingram Cancer Center.

“Diabetes and metabolic disturbances associated with insulin regulation are more common among African-Americans compared to Caucasians,” points out Jay H. Fowke, Ph.D., an assistant professor of medicine and cancer epidemiologist at the cancer center. “Metabolic disorders associated with obesity and diabetes may lower PSA levels and may cause a delay in referring a patient for a biopsy. This may be in part why we often don’t detect prostate cancer in African-American men until it is already fairly advanced.”

The researchers examined participants in the Southern Community Cohort Study, an NCI-funded initiative that monitors the health of 90,000 men and women between 40 and 79 years throughout the southern U.S. The researchers randomly selected 121 African-American men and 121 Caucasian men. Each group had the same proportion of obese and overweight men. Study participants had no prior diagnosis of cancer or diabetes.

From each participant’s blood sample, the scientists compared PSA levels with the amounts of HbA1c, C-peptide, leptin, and adiponectin, all naturally occurring blood-borne molecules that have a biological role in metabolism, insulin activity, or the function of fat cells.

Among African-Americans, PSA levels were 50% lower among men with higher levels of C-peptide, a biomarker that reliably indicates an increase in insulin, the team reports. This association was especially prevalent among obese African-American men, they add. PSA levels also declined somewhat among obese Caucasian men with high C-peptide levels, but this relationship was not as strong as it was in the African-American group.

The researchers saw a similar pattern in Caucasian men regarding the diabetes biomarker HbA1c, where PSA levels were 50% lower among those with higher levels of HbA1c. PSA levels were not associated with HbA1c in the African-American group.

The results were reported on November 28 at the American Association for Cancer Research conference on “The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved.”

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