A First Report of <u>Incidence Rates</u> (Not Prevalence) by Breast Cancer Subtypes.
Authors: M. Lund, M. Lund, M. Lund, E. Butler, B. Hair, K. Ward, K. Ward, J. Andrews, J. Andrews, A. Bayakly, S. Gabram, R. O'Regan, J. Eley
Journal: Cancer Research (2009)

Abstract BackgroundWe and others have recently repeatedly documented that among women diagnosed with invasive breast cancer in the U.S., the majority of cancers (based on clinical evaluation of the Estrogen Receptor (ER), Progesterone Receptor (PR) and Her2-neu (HER2) expression) classify as ER positive(+)/PR+HER2 negative(-), (50-70%). HER2+ breast cancers represent another 10-20% of all diagnosed breast cancers and Triple Negative (ER-PR-HER2-) cancers 12-20%. It is also now widely accepted that these prevalences vary by race and age, with young and black women most likely to be diagnosed with Triple Negative tumors—reasons for which remain unexplained. However, to our knowledge, no one has reported actual incidence rates for the breast cancers by the subtypes described above. We report the first incidence rates for breast cancer subtypes overall (and by race and age groups) and extrapolite new annual case burdens.MethodsAfter identifying invasive breast cancer cases through the Surveillance Epidemiology End Results (SEER) cancer registry, case medical records and cancer registry abstracts were investigated to determine ER, PR, and HER2 status among 1842 female residents of two large metropolitan Atlanta counties (Fulton and Dekalb) diagnosed with breast cancer during 2003-2004 (52.5% White, 44.2% Black, 1.6% Hispanic, and 1.7% 'Other'). Four triple subtypes were defined, based on positive (+) or negative (-) expression of ER, PR, and HER2: ER-PR-HER2- (Triple negative), ER-PR-HER2+, ER+/PR+HER2-, and ER+/PR+HER2+. SEER prep and SEER stat were used to calculate age adjusted incidence rates per 100,000, based on the 2000 U.S. census data representing our study population.ResultsTable 1. Age-adjusted Incidence Rates* of Women Diagnosed with Primary Invasive Breast Cancer by Triple Subtypes, Atlanta, GA 2003-2004 All breast cancersTriple NegativeER-PR- HER2+ER+/PR+ HER2+ER+/PR+ HER2-Unknown SubtypeAll women176.027.88.912.298.928.2 White179.319.47.512.6110.729.0Age&amp;lt;5066.38.73.27.637.79.0Age50+357.936.414.420.5226.160.5 Black171.236.310.012.186.726.1Age&amp;lt;5069.615.75.77.428.112.7Age50+331.869.016.919.5179.247.2 *Rates per 100,000 and adjusted to the 2000 U.S. population census for Fulton-Dekalb counties, Atlanta, GA.ConclusionTriple negative incidence rates differ markedly with rates for black women nearly double those for white women, regardless of age, and at the expense of the more treatable ER+/PR+Her2- tumors. Incidence rates, though, are highest for ER+/PR+ HER2- breast cancer among both black women and white women ages 50 and over. Our overall incidence rates representing two large metropolitan Atlanta counties are comparable to the SEER 9 area U.S. rates for the same time period among women ages 50+. However our rates are higher for women under age 50. Thus, the triple negative incidence rates we report can be cautiously extrapolated to an annual burden of new U.S. triple negative cases of 5,000 for black women and 16,000 for white women. Variations in actual incidence rates of breast cancer subtypes warrant in-depth population-based explorations. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3065.