HER2 testing being neglected in patients with breast cancer

NEW YORK (Reuters Health) - Many women with breast cancer who could benefit from the monoclonal antibody trastuzumab (Herceptin) are not receiving it, while other women are treated with trastuzumab even though they've never been tested to see if their tumors are likely to respond.

"The limited evidence available suggests that there are important variations in testing practices and key gaps in knowledge about those practices," Dr. Kathryn A. Phillips from the University of California, San Francisco, and her colleagues report in the September 14 online issue of Cancer.

Dr. Phillips and her team reviewed the medical literature to determine the extent of testing for human epidermal growth factor receptor 2 (HER2) in clinical practice in the US.

In one cohort of metastatic breast cancer patients treated in a single large health system in 1999/2000, only 52% were tested for HER2. In a separate cohort of Medicare patients with newly diagnosed invasive breast cancer in 2005, only 32% were tested.

Furthermore, according to the researchers, unreported 2005 data from UnitedHealthcare indicates that 12% to 20% of women receiving trastuzumab had inconclusive evidence - and in some cases, no evidence even of a test - for HER2 overexpression. Not only were these women likely to be receiving ineffective treatment, the authors point out, but they were also increasing their risk of heart failure, at an estimated cost to the healthcare system of about $100,000 annually.

The investigators also note that about 20% of HER2 tests performed by community labs were incorrect, based on comparison to central or reference labs.

"Despite the clinical success of trastuzumab, there is...uncertainty regarding the most appropriate and efficient testing strategy and...the interpretation of test results," the researchers note.

It's therefore crucial, they conclude, that discoveries in human genomics be accompanied by translational research to help move these advances into real world clinical settings, "in a manner that maximizes health benefits and minimizes harm to individual people and populations."

Cancer 2009.

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