Experts claim breast cancer isn't a single disease but instead consists of four major molecular subtypes.

The new report published March 30 in the Journal of the National Cancer Institute was compiled by a group of leading medical experts from the North American Association of Cancer Registries (NAACCR), the U.S. Centers for Disease Control and Prevention (CDC), the American Cancer Society and the National Cancer Institute (NCI).

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Each of the four subtypes varies by age, race/ethnicity, poverty level and many other factors. Incidences of these subtypes take different treatment responses and survival rates.

For the report, researchers analyzed the incidence of invasive breast cancer among women with ages 85 and below using 2011data from the NAACCR member registries.

The NAACCR registries record breast cancer incidence by four tumor subtypes: the Luminal A (HR+/HER2-), Luminal B (HR+/HER2+), HER2-enriched (HR-/HER2+) and triple-negative (HR-/HER2-).

The subtypes are defined by the status of the hormone receptor (HR) and the HER2 gene expression.

For the first time, researchers were able to observe how the incidence of each breast cancer subtype differs by a number of factors.

The findings reveal the least aggressive subtype, HR+/HER2-, was prevalent among non-Hispanic white women. For various racial/ethnic groups, the researchers found the rates of this subtype decreased as poverty levels rose.

In addition, non-Hispanic blacks had higher incidence rates of the most aggressive subtype, the triple negative breast cancer, compared to other racial/ethnic groups.

For all the subtypes, non-Hispanic blacks also had the highest rates of disease at late stage. Researchers said this was linked to lower survival and corresponded to the record of blacks having highest number of deaths.

When looking at the findings by age, researchers found the rates of HR+/HER2- breast cancer were comparable across all racial/ethnic groups for women below the age of 45.

National Cancer Institute director Dr. Harold Varmus said the report that assesses breast cancer as for defined subtypes and not as a single disease is a welcome step and a medically important information that guides therapeutic strategies.

Dr. Varmus added that the newly defined diagnostic categories will help prevent and treat breast and many other cancers, as well as assess their incidence and outcomes more rigorously over time.

Tagsbreast cancer