They found no link between diabetes and prostate cancer progression. But in a secondary analysis, after sorting the data by race and weight, investigators found an association between diabetes and an increased risk of recurrence and a trend toward more aggressive recurrence (reflected in a shorter doubling time of the PSA) -- but only among obese white men. In all other subgroups, diabetes was associated with lower recurrence risk and longer PSADT.

"We really don't know what mechanisms might be in place that could account for this relationship," says Freedland. "But consider this: diabetes is associated with low levels of insulin and testosterone, an inhospitable environment for tumor growth. This is compounded in obese white men who also have lower insulin-like growth factor levels. The thinking is that if a tumor is powerful enough to grow in such a hostile environment, then it's probably a pretty aggressive one."

Freedland says this is the first study to examine racial and body weight differences in the association between diabetes and prostate cancer progression, so these findings need to be validated before drawing firm conclusions regarding any relationships. Because all men in the study were healthy enough to undergo surgery also means that the results may not be applicable to a general population.

Source: Duke University Medical Center