ATLANTA — Elevated C-peptide and hemoglobin A1c levels were associated with low levels of prostate-specific antigen in obese, nondiabetic black and white men in a cross-sectional study.
PSA levels were approximately 50% lower among black men with higher levels of C-peptide, a biomarker of insulin, whereas among white men, PSA levels were lower with increasing levels of HbA1c, a marker of blood glucose control, said Jay H. Fowke, Ph.D., at a conference sponsored by the American Association for Cancer Research.
Such metabolic disturbances may mask the presence of prostate cancer and delay a diagnosis until the cancer is too advanced for successful treatment, said Dr. Fowke of Vanderbilt University, Nashville, Tenn.
A number of studies have looked at obesity and PSA levels, and some findings have suggested that obese men have lower PSA levels. Black men are more likely than white men to be diagnosed with advanced prostate cancer and have a poorer prognosis following treatment.
Dr. Fowke and his Vanderbilt colleagues looked at the biomarkers associated with obesity to see if there was a link between them and lower PSA levels.
They selected at random 121 black men and a similar number of white men who were participants in the Southern Community Cohort Study, a National Cancer Institute-funded initiative that monitors the health of 90,000 men and women between the ages of 40 and 79 years throughout the southern United States.
The proportion of obese and overweight men was the same in each group, and none of the men had a prior diagnosis of prostate cancer or diabetes.
Blood samples from each participant were analyzed for C-peptide and HbA1c, as well as leptin and adiponectin.
There were “subtle” differences between black and white men, Dr. Fowke said.
PSA levels did not significantly differ across leptin or adiponectin levels, but were 50% lower among black men with higher C-peptide levels. This association was especially prevalent among obese black men, he noted.
In contrast, C-peptide was not associated with PSA level among white men. In this group, PSA levels were 50% lower in men with higher levels of HbA1c.
The association between HbA1c and PSA seemed to be stronger among white men with a body mass index of less than 30 kg/m
The finding suggests that there may be differences between white and black men in the way PSA responds to obesity.
In an interview, Dr. Fowke said these are basic research findings that do not indicate a need to change current screening recommendations. However, the findings do suggest that clinicians who manage obese and overweight patients should be aware that PSA level may not be as sensitive for the detection of prostate cancer in these patients.
“They may want to put more emphasis on a digital rectal exam, for example. Or they might want to follow these patients more carefully and do PSA velocity testing to see if there is a large change in PSA values over time.”
Dr. Fowke said he had no conflicts of interest to declare. The study was sponsored by the National Cancer Institute.
Physicians might want to do PSA velocity testing to see if there is a large change in PSA values over time. DR. FOWKE