| Study, year | Patients (N) | Outcomes |
| Nirmul, 1982 [14] | 16 | -Study design: case-control of 8 MBC cases of ductal carcinoma and 8 controls to analyze the sex-hormone profile of MBC patients -No significant difference in the mean fasting levels and ranges of LH, FSH, PRL, DHEA-S, and SHBG in the cases when compared to the controls -Mean total serum estradiol-17β level and calculated mean free estradiol index increased in cases (p < 0.02) |
| Casagrande, 1988 [18] | 150 | -Study design: case-control of 75 cases and 75 controls to investigate suspected risk factors -Men who weighed ≥90 kg at age 30 had >5x the breast cancer risk of men weighing <60 kg at that age (RR = 5.45 and RR = 1.00, respectively, p = 0.04) -No significant difference observed between cases and controls with respect to frequency of alcohol consumption -Gynecomastia was not found to be a significant risk factor |
| Hsing, 1998 [19] | 690 | -Study design: case-control study of 178 MBC mortalities and 512 male controls who died of other causes to investigate risk factors -Increased risk for men described as having been very overweight (OR = 2.3, 95% CI: 1.1 - 5.0) -Dose-response relationship seen between risk and BMI (p < 0.01) -No association found for alcohol use |
| Sorensen, 1998 [20] | 11,642 | -Study design: males with a diagnosis of liver cirrhosis followed for a mean of 4.3 years to assess risk of breast cancer and men with cirrhosis -3 cases observed (SIR = 4.0, 95% CI: 0.8 - 11.7) |
| Ewertz, 2001 [23] | 624 | -Study design: population-based case-control study of 156 cases and 468 controls -Increased risk of MBC associated with obesity 10 years before diagnosis (OR = 2.1; 95% CI: 1.0 - 4.5), and diabetes (OR = 2.6, 95% CI: 1.3 - 5.3) |
| Altinli, 2002 [24] | 40 | -Study design: retrospective review of all MBC patients who underwent surgery to examine relation between BMI and MBC -Average BMI = 26.54 kg/m2 (above the World Health Organization upper limit of normal) -23 (57.5%) out of 40 patients were above their ideal body weight (statistical evaluation not performed due to small sample size) |
| Johnson, 2002 [25] | 1986 | -Study design: analysis of risk factors in a population-based case-control study of 81 newly diagnosed, histologically confirmed MBC cases and 1905 male controls -Increased risk of MBC in overweight cases (OR = 2.19, 95% CI: 1.08 - 4.43) |
| Olsson, 2002 [26] | 446 | -Study design: prospective cohort study of men with histological diagnosis of gynecomastia -No new cases of MBC seen at the end of median follow-up time (266 months) |
| Guenel, 2004 [13] | 1506 | -Study design: case-control study of 74 histologically verified MBC cases and 1432 age-matched controls to investigate the role of alcohol drinking in MBC -Risk of MBC increased by 16% (95% CI: 7 - 26) per 10 grams of alcohol per day (p < 0.001) -OR = 5.89 (95% CI: 2.21 - 15.69) for alcohol intake >90 grams/day |
| Brinton, 2008 [16] | 324,920 | -Study design: prospective NIH-AARP Diet and Health Study, of 121 MBC patients -Obesity was positively related to risk (RR = 1.79, 95% CI: 1.10 - 2.91, for BMI >30 vs< 5 kg/m2) and physical activity inversely related, even after adjustment for BMI |
| Brinton, 2010 [15] | 4,501,578 | -Study design: MBC etiologic factors assessed from 642 cases of primary MBC documented in the U.S. Veterans Affairs medical care database -Medical conditions related to MBC risk: diabetes (RR = 1.30, 95% CI: 1.05 - 1.60), obesity (1.98, 1.55 - 2.54), orchitis/epididymitis (1.84, 1.10 - 3.08), Klinefelter’s syndrome (29.4, 12.26 - 71.68), gynecomastia (5.86, 3.74 - 9.17) -Cholelithiasis an MBC risk for black patients (RR = 3.45, 95% CI: 1.59 - 7.47) -After adjusting for obesity, the association between MBC and diabetes disappeared, but that between MBC and gynecomastia persisted |