Prostate cancer and diabetes

• among men of European ancestry, diabetics have a lower risk of prostate cancer than do nondiabetics
  • biological basis of this association is unknown
  • a population-based prospective study included 5,941 prostate cancer cases identified over a 12-year period (1993-2005) among 86,303 European-American, African-American, Latino, Japanese-American, and Native Hawaiian men from the Multiethnic Cohort
    • association between diabetes and prostate-specific antigen (PSA) levels (n=2,874) and PSA screening frequencies (n=46,970) was also examined
    • diabetics had significantly lower risk of prostate cancer than did nondiabetics (relative risk = 0.81, 95% confidence interval (CI): 0.74, 0.87; P<0.001), with relative risks ranging from 0.65 (95% CI: 0.50, 0.84; P=0.001) among European Americans to 0.89 (95% CI: 0.77, 1.03; P=0.13) among African Americans
    • mean PSA levels were significantly lower in diabetics than in nondiabetics (mean PSA levels, 1.07 and 1.28, respectively; P=0.003) as were PSA screening frequencies (44.7% vs. 48.6%; P<0.001); however, this difference could explain only a small portion (approximately 20%) of the inverse association between these diseases
  • the study authors concluded that diabetes is a protective factor for prostate cancer across populations, suggesting shared risk factors that influence a common mechanism.

A meta-analysis found an inverse association between diabetes mellitus and prostate cancer [RR, 0.84] (2)

• for cohort studies alone, the RR was 0.81

Jo et al showed a negative association with prostate cancer relating to duration of metformin treatment (3):

• prostate cancer risk decreased with increasing duration of metformin administration

References:

1. Waters KM et al. Association of diabetes with prostate cancer risk in the multiethnic cohort.Am J Epidemiol. 2009 Apr 15;169(8):937-45.
2. Kasper JS, Giovannucci E. A meta-analysis of diabetes mellitus and the risk of prostate cancer. Cancer Epidemiol Biomarkers Prev. 2006 Nov;15(11):2056-62. doi: 10.1158/1055-9965.EPI-06-0410. PMID: 17119028.
3. Jo JK, Song HK, Heo Y, Kim MJ, Kim YJ. Risk analysis of metformin use in prostate cancer: a national population-based study. Aging Male. 2023 Dec;26(1):2156497. doi: 10.1080/13685538.2022.2156497. PMID: 36974927.