Patterns of HER2 testing in the management of primary breast cancer

Background: Women with invasive breast cancer should be tested for human epidermal growth factor receptor-2 (HER2) status at the time of diagnosis. To date, no population-based patterns of use studies have examined demographic and clinicopathologic factors associated with decisions by clinicians to test patients. Methods: We reviewed summary pathology reports submitted to the Connecticut Tumor Registry for all Black/African American (B/AA) women (n = 644) and a 7% random sample (n = 720) of White women diagnosed in 2000–2003 with primary invasive breast carcinoma. Receipt of a HER2 test (yes vs. no) was examined in relation to patient race, age, socioeconomic status, year of diagnosis, estrogen receptor (ER) status, tumor grade, lymph node status, size and stage at diagnosis. Results: A greater proportion of tumors from B/AA patients were tested compared to those of White women (69.5% vs. 61.9%, p < 0.05). Tumors of patients under the age of 60 were 1.50-times more likely than older women to have been tested, and B/AA women were 1.40-times more likely than White patients to be tested. HER2 testing was more likely to be observed when information also was reported about ER status (OR = 15.9, p < 0.001), tumor grade (OR = 2.28, p < 0.05), tumor size (OR = 2.16, p < 0.05), and lymph node status (OR = 2.06, p < 0.05). Conclusions: Variation in which breast cancer patients received HER2 testing appears to reflect expectations about a woman's prognosis. Discrepancies in receipt of testing deserve further study as current guidelines call for all tumors to be assessed in order to adequately characterize prognosis and determine eligibility for HER2-targeted therapy.