Table 1.
Epidemiological studies on the effect of metformin on prostate cancer incidence.
| Author (Country) | Period | No. Cases/ Controls |
Risk Estimates (95% CI) | Adjusted Variables |
|---|---|---|---|---|
| Preston (Denmark) [48] | 1989–2011 | 12,226/122,260 | Adjusted OR: 0.84 (0.74–0.96) | CCI, diabetic complications, marital status, use of PPI, statin, 5αRI |
| Haring (Finland) [49] | 1996–1999 | 7681/1080 | HR: 0.80 (0.67–0.96) | age, use of antihypertensives, cholesterol-lowering drugs, 5αRI, α-blockers, NSAIDs, aspirin |
| Ruiter (Netherlands) [50] | 1998–2008 | 52,698/32,591 | HR: 0.90 (0.88–0.91) | Age, sex, number of unique other drugs, number of hospitalizations, calendar time |
| Feng (REDUCE Study Group) [51] | 2003–2009 | 194/205 | Overall OR: 1.19 (0.72–1.99) Low-grade PCa OR: 1.01 (0.57–1.81)High-grade PCa OR: 1.83 (0.75–4.46) |
Age, race, geographic region, PSA, prostate volume, digital rectal examination, BMI, family history of PCa, coronary artery disease, smoking, aspirin, NSAIDs, statin |
| Chen (Canada) [52] | 1994–2012 | 35,829/44,172 | Adjusted HR in non-Chinese men aged 50–59: 0.86 (0.74–1.00) aged 60–69: 1.00 (0.90–1.12) aged >70: 1.13 (0.99–1.29) |
Socioeconomic class, use of other diabetes medications, dipeptidyl peptidase IV inhibitors, glucagon-like peptide 1 receptor agonists, thiazolidinediones, insulin |
| Wang (US) [53] | 2003–2012 | 23,130/36,776 | Non-Hispanic white HR: 0.91 (0.82–1.01) African American HR: 1.10 (0.94–1.27) Hispanics HR: 0.63 (0.49–0.80) |
Age, race, CCI, BMI, LDL, HbA1c, PSA |
| Raval (US) [54] | 2008–2009 | 948/1704 | Unadjusted OR: 0.69 (0.49–0.95) Adjusted OR: 0.68 (0.48–0.97) |
Age, race, marital status. |
| Nordstrom (Sweden) [55] | 2007–2012 | 7678/177,989 | Any PCa OR: 1.013 (0.816–1.257) High-grade PCaOR: 1.207 (0.936–1.557) |
Age, log-transformed PSA level, PSA quotient, comorbidity, educational level, medication use |
| Onitilo (Australia) [56] | 1995–2009 | NA | HR: 0.86 (0.72−1.03) | HbA1c, glucose-lowering medication use (insulin, metformin, sulfonylurea), age, BMI, insurance status, comorbidities, smoking history, location of residence |
| Tseng (Taiwan) [57] | 1998–2002 | 186,212/209,269 | HR: 0.362 (0.345–0.380) | Age, PSA, comorbidities, obesity, other cancers |
BMI: body mass index; CCI: Charlson Comorbidity Index; CI: confidence interval; 5αRI: 5alpha reductase inhibitor; HbA1c: hemoglobin A1c; HR: hazard ratio; LDL: low-density lipoprotein; NA: not applicable; NSAIDs: nonsteroidal anti-inflammatory drug; OR: odds ratio; PCa: prostate cancer; PSA: prostate-specific antigen; PPI: proton pump inhibitor.