HER2 testing and subsequent trastuzumab treatment for breast cancer in a managed care environment.

BACKGROUND: Degree of physician adherence to 2001 guidelines recommending routine testing of human epidermal growth factor receptor 2 (HER2) status among newly diagnosed, recurrent, and metastatic breast cancer (BC) cases, and frequency of trastuzumab use in HER2-positive patients are not well documented.
METHODS: Patients newly diagnosed with BC managed by an identifiable hematologist/oncologist between June 1, 2005 and June 30, 2006 were identified from an administrative claims database of three health plans (n = 3,521). From these, a subset of 380 patients was identified for medical chart review. HER2 testing (occurrence, type of test used), HER2 status (positive, negative, unknown), and trastuzumab usage were evaluated.
RESULTS: HER2 testing occurred in 88% of all newly diagnosed patients with BC and in 98.1% of those with stage 1 or higher breast cancer (n = 322), for whom testing is recommended. Among those with HER2 testing performed (n = 335), 21.5% were positive (HER2(+)), 77.3% were negative (HER2(-)), and 1.2% were unknown. Of the 52 patients who used trastuzumab, only one patient did not have documented HER2 overexpression. Of the 45 HER2(+) women who had stage 2 or higher BC, 13% did not receive trastuzumab.
CONCLUSIONS: HER2 testing status was extremely high among newly diagnosed BC patients treated by hematologists/oncologists in a managed care environment. There was almost no evidence of inappropriate prescribing of trastuzumab, but 1 of every 7.5 patients with HER2-overexpressing stage 2 or higher breast cancer did not receive the agent.