A new study published on March 30 in the Journal of the National Cancer Institute has the potential to significantly improve breast cancer treatment. The study authors report that for the first time, they have determined the incidence of the four major breast cancer by reviewing national data. As a result, for the first time, they have categorized breast cancer by age, race/ethnicity, poverty level, and several other factors. They note that the four subtypes respond differently to treatment and have different survival rates; thus, this new information will aid researchers in more accurately classifying stratify breast cancer by clinically relevant degrees of risk. As a result, it has the potential to improve breast cancer treatment. In addition, women who are apprised of this information will be able to better understand the consequences for their health based on their breast cancer subtype.
The report, titled The Annual Report to the Nation on the Status of Cancer, 1975-2011 revealed continuing declines in cancer deaths for both men and women, for children, and for almost all major cancer sites. The report was co-authored by scientists from the North American Association of Central Cancer Registries (NAACCR), the American Cancer Society (ACS), the Centers for Disease Control and Prevention (CDC), and the National Cancer Institute (NCI) at the National Institutes of Health.
Breast cancer subtypes have major effects on the determination of the best treatment strategy and may hold important clues to the development of breast cancer. There are four molecular subtypes, which can be classified by their hormone receptor (HR) status and expression of the HER2 gene: Luminal A (HR+/HER2-), Luminal B (HR+/HER2+), HER2-enriched (HR-/HER2+), and triple negative (HR-/HER2-). Now, these subtypes are being recorded by cancer registries throughout the nation; thus, providing statisticians with the ability for the first time to comprehensively assess breast cancer rates based on clinically meaningful subtypes.
The new report suggests that some of the differences in rates of breast cancer incidence and mortality that are found among racial and ethnic groups are related to differences in the incidence of different subtypes. Geographic variation in rates that the authors determined were based on multiple factors, including underlying demographic patterns, regional cultures and associated behaviors, as well as healthcare access.
The authors discovered unique racial/ethnic group-specific patterns by age, poverty level, geography, and by specific tumor characteristics. The rates of HR+/HER2- breast cancer, which is the least aggressive subtype, were highest among non-Hispanic whites. The rates of HR+/HER2- breast cancer decreased with increasing levels of poverty for every racial and ethnic group. In addition, similar to what had been reported in previous studies, non-Hispanic blacks had higher incidence rates of triple negative breast cancer, the most aggressive subtype, than other racial/ethnic groups. Among all the subtypes, non-Hispanic blacks also had the highest rates of late-stage disease and of poorly/undifferentiated pathology. All of these factors are linked to lower survival and correspond with blacks having the highest rates of breast cancer deaths.
The report also details trends in incidence and death rates of many major cancers and all cancers combined. Overall cancer incidence, new cancer cases, continued to decrease in men, remained stable in women, and increased in children. The researchers also found that there has been a relatively consistent decline in overall cancer mortality rates since the early 1990s; rates from 2002 to 2011 decreased by about 1.8% per year among males and by 1.4% per year among females. Among children up to 19 years of age, mortality rates have continued to decrease since 1975, with the exception of the period between 1998 and 2003.
For the most recent reporting period, the rate of decline in lung cancer incidence and mortality has accelerated in both men and women, most likely reflecting sustained public health efforts to decrease smoking rates. Colorectal cancer incidence and mortality among both men and women, and prostate cancer incidence and mortality in men, continue the downward trends seen in previous years.