Abstract P3-12-12: HER2 Evaluation in Relation to Breast Cancer Treatment Decisions in a Managed Care Plan

Abstract

Abstract Background: In 18-20% of breast cancer tumors, the human epidermal growth factor receptor 2 (HER2) gene is abnormally amplified with increased expression of the associated protein. HER2 amplification is associated with rapid tumor proliferation, shorter disease-free survival, and poorer overall survival. Because women with HER2 amplification are more likely to benefit from treatment with the drug trastuzumab, testing for HER2 is recommended to guide therapy. However, little is known about HER2 testing practices and associated treatment in real-world settings. This study examined uptake, use, and appropriateness of HER2 testing, and the relationship between HER2 test results and treatment decisions in a large integrated health system. Methods: We identified 3,634 patients with primary breast cancer diagnosed from 1998-2007 who were members of the Kaiser Permanente Northwest health plan. We collected data on patient and tumor characteristics, HER2 testing status, test results, and trastuzumab treatment from tumor registry and pharmacy datasets. We defined women as evaluated for HER2 if they received HER2 testing by immunohistochemistry (IHC) and/or fluorescent in-situ hybridization (FISH). We manually abstracted medical charts for a subset of patients to verify findings and investigate anomalies. We compared testing and treatment results to professional guidelines. Results: From 1998-2000, the percentage of patients with invasive breast cancer who underwent HER2 evaluation increased from 12% to 94%; from 2000-2007, 94% (2304/2461) received HER2 testing over all years combined. In most cases, an equivocal or positive IHC test was followed by FISH. Only 2.4% of women with ductal carcinoma in situ (13/538), for whom HER2 testing is not recommended, were tested, and the proportion remained consistently low over the entire study period. Trastuzumab use increased five-fold after 2004, when guidelines expanded to include recommending adjuvant treatment for early-stage breast cancer in addition to metastatic treatment. Ninety-five percent of women receiving trastuzumab had a positive HER2 result, while the remainder had equivocal HER2 results or received treatment outside thedelivery system. After 2004, 55% of women with invasive breast cancer and overexpression of HER2 received trastuzumab treatment; this ranged from 44% of women with localized breast cancer to 80% of women with distant metastatic disease. We estimate that, after correcting for errors in the datasets, professional guidelines were followed for over 97% of patients diagnosed since 2000. Conclusions: Kaiser Permanente Northwest is systematically performing HER2 evaluation on patients with invasive breast cancer, and the information is used to make appropriate treatment decisions. This information should be gathered in other health care settings for comparison. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-12-12.