Review of HER2 Testing in Clinical Practice

There is a paucity of information about HER2 testing of breast cancer patients in clinical practice.

A literature review discussed how and what evidence might be improved to help guide decisions regarding emerging tests and associated therapies in cancer care. The review suggested that many breast cancer patients who might benefit from trastuzumab are not receiving it, and that some women receiving the drug have never been tested for the receptor it targets.

Kathryn A. Phillips, Ph.D., at the Helen Diller Family Comprehensive Center, University of California, San Francisco (USA), and colleagues reviewed the literature related to use of HER2 testing in clinical practice. The review appeared online in the September 14, 2009 issue of Cancer, journal of the American Cancer Society.

Standard care dictates that women with early-stage breast cancer should be tested to see if they have tumors that express the HER2 protein. Those who test positive are candidates for treatment with trastuzumab, which is only effective in HER2-positive cancers.

Dr. Philips and her colleagues reported that up to two-thirds of patients eligible for HER2 testing had no documentation of a test in their health insurance records. About one in five women who received trastuzumab had no documentation of a positive HER2 test in their health insurance records. The studies also revealed that about one in five HER2 test results might be incorrect. However, the scientists said that the findings do not support a case for slowing the diffusion of new technology in clinical practice.

The authors also found that studies examining economic issues associated with prescribing trastuzumab often did not consider the role of HER2 testing, which can have a substantial impact on the cost-effectiveness of the therapy. Given the increasing use of costly targeted therapies proper testing will become more important to ensure that medications are directed only to the patients who will benefit from them.

"There is little evidence about the use of HER2 testing in routine clinical practice that can inform the current debate about selection of patients for treatment or the relative advantages and disadvantages of alternative testing strategies," the authors concluded. "The limited evidence available suggests there are important variations in testing practices and key gaps in knowledge about those practices."

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Helen Diller Family Comprehensive Center, University of California San Francisco