Metformin for Reducing Racial/Ethnic Difference in Prostate Cancer Incidence for Men with Type II Diabetes.

Racial/ethnic disparity in prostate cancer is under studied in men with diabetes who are at a higher risk of aggressive prostate cancer. This study assessed the race/ethnic disparity in prostate cancer incidence for men with type II diabetes (T2D) and whether the impact of metformin on prostate cancer incidence varied by race/ethnicity. We conducted a retrospective study in 76,733 male veterans with T2D during 2003 to 2012. Cox proportional hazards model adjusting for covariates and propensity scores of metformin use and race/ethnic group membership was utilized to compute the HR of prostate cancer incidence associated with race/ethnicity and compare HR associated with metformin use between race/ethnic groups. Mean follow-up was 6.4 ± 2.8 years; 7% were Hispanics; 17% were African Americans (AA); mean age was 67.8 ± 9.8 years; 5.2% developed prostate cancer; and 38.9% used metformin. Among these diabetic men without metformin use, prostate cancer incidence was higher in Hispanics and AA than in non-Hispanic White (NHW). Use of metformin alone or metformin + statins was associated with a greater prostate cancer incidence reduction in Hispanics compared with NHW, but not between AA and NHW. Use of metformin + finasteride was associated with a greater prostate cancer incidence reduction in Hispanics and AA compared with NHW. Our results suggested that metformin treatment could be a potential strategy to reduce prostate cancer incidence in the minority populations who are at high risk for fatal prostate cancer. It will be important to further examine the pleiotropic effects of metformin in multi-race/ethnic prospective studies to better inform clinical management and potentially reduce racial/ethnic disparity in prostate cancer incidence among diabetic men. Cancer Prev Res; 9(10); 779-87. ©2016 AACR.

Wide disparity in genetic admixture among Mexican Americans from San Antonio, TX.

We studied 706 participants of the San Antonio Family Diabetes Study (SAFDS) and 586 male samples from the San Antonio Center for Biomarkers of Risk of Prostate Cancer (SABOR) and used 64 ancestry informative markers to compare admixture proportions between both groups. Existence of population substructure was demonstrated by the excess association of unlinked markers. In the SAFDS sample, ancestral proportions were estimated at 50.2 ± 0.6% European, 46.4 ± 0.6% Native American, and 3.1 ± 0.2% West African. For the SABOR sample, the proportions were 58.9 ± 0.7%, 38.2 ± 0.7%, and 2.9 ± 0.2%, respectively. Additionally, in the SAFDS subjects a highly significant negative correlation was found between individual Native American ancestry and skin reflectance (R(2) = 0.07, P= 0.00006). The correlation was stronger in males than in females but clearly showed that ancestry only accounts for a small percentage of the variation in skin color and, conversely, that skin reflectance is not a robust surrogate for genetic admixture. Furthermore, a substantial difference in substructure is present in the two cohorts of Mexican American subjects from the San Antonio area in Texas, which emphasizes that genetic admixture estimates should be accounted for in association studies, even for geographically related subjects.