Breast cancer is no longer the monolithic disease it once was. And now, depending on the type of breast cancer a patient has, appropriate treatment is getting easier. According to the Annual Report to the Nation on the Status of Cancer, 1975-2011, released by the National Cancer Institute (NCI) in Bethesda, Maryland, there are data on the national incidence of the 4 major molecular subtypes of breast cancer by age, race and ethnicity, socioeconomic level, and other factors for the first time.
Although the subtypes—which relate to the hormone receptor (HR) status and expression of the HER2 gene—were already known prior to the report, incidence was not. But beginning in 2010, cancer registries have been required to report both HR and HER2 status for breast cancer cases. Being able to divide the data in previously unavailable ways will help researchers more accurately stratify breast cancer by risk, NCI says.
The least aggressive breast cancer subtype, HR+/HER2- was the most prevalent, at 73% of all breast cancer cases. Rates were highest among non-Hispanic whites living in low-poverty areas.
“Triple-negative” breast cancer, HR-/HER2-, made up 13% of all cases and had the worst prognosis. Non-Hispanic blacks had the highest rates of triple-negative breast cancer, as well as the highest rates of late-stage disease and poorly/undifferentiated pathology.
The HR+/HER2+ breast cancer, which accounted for 10% of all cases, was more common in Idaho, Tennessee, and Pennsylvania. No states were statistically different from the national rates for HR-/HER2+, which accounted for 5% of all cases. Triple-negative rates were lower in the northwestern U.S. and higher in the southeastern U.S.
The data can also be used to help women better understand health implications based on their breast cancer subtype. In one study cited by NCI, slightly more than half of the women reported their correct estrogen status, HER2 status, and stage of cancer. Only about 1 in 5 reported the correct grade. However, women who understood the basis for their treatment, the researchers found, were generally more satisfied with treatment.
National Cancer Institute. New analysis of breast cancer subtypes could lead to better risk stratification; Annual Report to the Nation shows that mortality and incidence for most cancers continue to decline [press release]. Bethesda, MD: National Cancer Institute; March 30, 2015.
National Cancer Institute. Annual Report to the Nation on the Status of Cancer, 1975-2011. Bethesda, MD: National Cancer Institute; 2015.
National Cancer Institute. Annual Report to the Nation on the Status of Cancer, 1975 -2011: questions and answers [press release]. Bethesda, MD: National Cancer Institute; March 30, 2015.