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||PROSPECTIVE EVALUATION OF RISK FACTORS FOR MALE BREAST CANCER in: Abstracts of the 41st Annual Meeting of the Society for Epidemiologic Research
||Brinton L, Richesson D, Gierach G, Lacey J Jr, Park Y, Hollenbeck A, Schatzkin A
||Am J Epidemiol
||2008 Jun 1
||Male breast cancer is extremely uncommon, accounting for only 0.7% of allbreast cancers. Identification of risk factors has been difficult, with mostresults deriving from small case-control studies that are subject to recallbiases. In the NIH-AARP Diet and Health Study, we prospectively assessedrisk factors among 324,928 men, ages 50-71 years, recruited during 1995-1996. In follow-up through December 2003, 121 male breast cancers (medianage = 68) were identified. Multivariable Cox proportional hazardsmodels were used to estimate relative risks (RRs) and 95% confidenceintervals (CIs). Obese subjects were at increased risk (RR and 95% CI =1.8, 1.1-2.9 for body mass index, BMI >30 vs. <25). Even after adjustmentfor BMI, there was some evidence of a protective effect of physical activity,with the RR being 0.49 (95% CI 0.28-0.87) for men who regularly engagedin lifting or climbing on their jobs. Men who reported a first-degree relative(male or female) with breast cancer were at a 1.9-fold increased risk (95%CI 1.2-3.1). Smokers were at somewhat higher risk than non-smokers,although there were inconsistent trends according to intensity and durationof smoking. Alcohol consumption was unrelated to risk. Of various medicalconditions examined, only a history of having had a bone fracture after theage of 45 related to risk (RR = 2.2, 95% CI 1.2-3.9). Diabetes was unrelatedto risk. The identified risk factors show some commonalities withfemale breast cancer and suggest the importance of hormonal mechanisms.Differences in risk factors (e.g., alcohol, fractures) may reflect uniquemechanisms associated with androgens and their ratio to bioavailableestrogens.