• Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta, Canada; Clinical Oncology Department, Ain Shams University, Cairo, Egypt. Electronic address: omar.abdelsalam@ahs.ca.

INTRODUCTION: The objective of this study was to assess family history links between breast cancer and prostate cancer in a prospectively collected cohort from the Prostate, Lung, Colorectal, and Ovary (PLCO) trial.

PATIENTS AND METHODS: This is a secondary analysis of the PLCO trial datasets. Eligible patients included female participants with complete information about prostate cancer family history and male participants with complete information about breast cancer family history. Multivariate Cox regression analysis was used to assess the impact of prostate cancer family history on breast cancer incidence and mortality. Likewise, multivariate Cox regression analysis was used to assess the impact of breast cancer family history on prostate cancer incidence and mortality.

RESULTS: A total of 45,807 female participants were eligible and included in the current study, and a total of 43,009 male participants were eligible and included in the current analysis. Within a multivariate Cox regression analysis, prostate cancer family history in a first-degree relative (FDR) was associated with a higher probability of diagnosis of breast cancer (hazard ratio [HR], 1.128; 95% confidence interval [CI], 1.007-1.265; P = .038); whereas it was not associated with a higher risk of death from breast cancer (HR, 1.065; 95% CI, 0.668-1.698; P = .791). Similarly, within a multivariate Cox regression analysis, breast cancer family history in an FDR was associated with a higher probability of diagnosis of prostate cancer (HR, 1.092; 95% CI, 1.011-1.180; P = .026) but not death from prostate cancer (HR, 0.442; 95% CI, 0.137-1.432; P = .173).

CONCLUSIONS: Female participants with a family history of prostate cancer in an FDR were more likely to develop postmenopausal breast cancer. Likewise, male participants with a family history of breast cancer in an FDR are at a higher probability of prostate cancer development. Risk correlation for premenopausal breast cancer could not be assessed owing to the nature of the PLCO study.