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

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.

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.

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.

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.