Incidence rates for hormone receptor positive (HR+) breast cancers are considerably higher in black men than white men, which is in stark contrast to lower incidence rates of those cancer subtypes in black versus white women to according to a new American Cancer Society appearing in the journal JNCI Cancer Spectrum.
In this study, researchers examined subtype specific breast cancer incidence rates in both black and white men in the U.S. using a contemporary nationwide database.
According to the study results, found that rates for all subtypes were higher among black than white men, with rates for HR+/HER- breast cancers about 41% higher among black men compared to white men; about 65% higher for HR+/HER2+, more than 2.5 times higher for HR-/HER2+, and 2.27 times higher for triple-negative breast cancer. Conversely, among women, rates in blacks were 21% lower for HR+/HER2- and comparable for HR+/HER2+, but 29% and 93% higher for HR-/HER2+ and triple-negative subtypes, respectively.
“Reasons for the elevated risk of breast cancer in black men are largely unknown but may involve multitude of risk factors including genetic and non-genetic factors,” the authors wrote according to a press release. Racial differences in the prevalence of mammography and menopausal hormone supplements are thought to have contributed to the historically higher incidence rate of HR+ cancers in white women, but these are not factors in breast cancer in men.
Well-known risk factors for male breast cancer include family history of breast and/or ovarian cancers, pathogenic mutations in BRCA2, radiation exposure, and conditions that alter hormonal balance such as Klinefelter syndrome and gynecomastia, and potentially obesity and diabetes. Moreover, previous studies have found higher level of estradiol was found to be associated with increased risk of male breast cancer after controlling for body mass index, suggesting a presence of estrogen-mediated carcinogenesis in male breast cancer. However, whether associations of these risk factors vary by tumor subtypes remains unknown and should be considered in future etiologic studies.