Age/race differences in HER2 testing and in incidence rates for breast cancer triple subtypes

BACKGROUND:

Although US year 2000 guidelines recommended characterizing breast cancers by human epidermal growth factor receptor 2 (HER2), national cancer registries do not collect HER2, rendering a population‐based understanding of HER2 and clinical “triple subtypes” (estrogen receptor [ER] / progesterone receptor [PR] / HER2) largely unknown. We document the population‐based prevalence of HER2 testing / status, triple subtypes and present the first report of subtype incidence rates.

METHODS:

Medical records were searched for HER2 on 1842 metropolitan Atlanta females diagnosed with breast cancer during 2003‐2004. HER2 testing/status and triple subtypes were analyzed by age, race/ethnicity, tumor factors, socioeconomic status, and treatment. Age‐adjusted incidence rates were calculated.

RESULTS:

Over 90% of cases received HER2 testing: 12.6% were positive, 71.7% negative, and 15.7% unknown. HER2 testing compliance was significantly better for women who were younger, of Caucasian or African‐American descent, or diagnosed with early stage disease. Incidence rates (per 100,000) were 21.1 for HER2+ tumors and 27.8 for triple‐negative tumors, the latter differing by race (36.3 and 19.4 for black and white women, respectively).

CONCLUSIONS:

HER2 recommendations are not uniformly adhered to. Incidence rates for breast cancer triple subtypes differ by age/race. As biologic knowledge is translated into the clinical setting eg, HER2 as a biomarker, it will be incumbent upon national cancer registries to report this information. Incidence rates cautiously extrapolate to an annual burden of 3000 and 17,000 HER2+ tumors for black and white women, respectively, and triple‐negative tumors among 5000 and 16,000 respectively. Testing, rate, and burden variations warrant population‐based in‐depth exploration and clinical translation. Cancer 2010. © 2010 American Cancer Society.