Objectives: Several studies have identified prostate cancer family history as a risk factor for prostate cancer incidence, typically associated with a twofold to fourfold increase in risk. A family history of breast cancer has also been implicated. We investigated the associations between prostate cancer incidence and family histories of prostate and breast cancer, controlling for possible confounding due to environmental factors.
Methods: Data from the random sample-based Massachusetts Male Aging Study cohort (1987 to 1997) were used. Incidence rates were calculated as the number of cases per person-year of follow-up. Covariates were adjusted for using Poisson regression.
Results: Among 1149 men with an average of 8.7 person-years of follow-up, 57 were diagnosed with prostate cancer, 110 men reported a prostate cancer family history, and 157 reported a breast cancer family history. The age-adjusted relative risk (RR) of prostate cancer incidence associated with prostate cancer family history was 3.29 (95% confidence interval [CI] 1.82 to 5.94). No evidence of heterogeneity was found across age levels (P = 0.83). Additional adjusting for environmental factors such as smoking, alcohol use, body mass index, physical activity, education, sexually transmitted disease history, diet, and hormone levels yielded a slightly higher RR (3.78, 95% CI 1.96 to 7.28). No association with a family history of breast cancer was evident (RR = 1.18, 95% CI 0.51 to 2.43).
Conclusions: We found an association between prostate cancer incidence and a family history of prostate cancer, independent of environmental factors. No association with a family history of breast cancer was evident.