HER2-positive breast cancers have too many copies of the HER2/neu gene. HER2-positive breast cancers make too much of the HER2 protein, which receives signals telling the breast cancer to grow. About 1 out of every 4 breast cancers is HER2-positive.
HER2-positive breast cancers tend to be more aggressive than HER2-negative breast cancers. Herceptin (chemical name: traztuzumab) and Tykerb (chemical name: lapatinib) are targeted therapy medicines used to treat HER2-positive breast cancers. Figuring out the HER2 status of a breast cancer is an important first step in deciding if these targeted therapies may be a good treatment option.
This study evaluated the results from a number of earlier studies. The researchers found that HER2 testing as well as the way the test results were recorded in medical and insurance records were inconsistent and generally inadequate.
In many cases:
In one earlier study, most women (90%) had only an IHC (immunohistochemistry) HER2 test performed, which is the less reliable type of HER2 test. The results weren't confirmed by the more reliable FISH (fluorescence in situ hybridization) test. When IHC test results are considered "borderline," experts recommend that a FISH test be done to determine HER2 status.
If you've been diagnosed with breast cancer, the information in your pathology report -- including HER2 status -- gives your doctor important details about the "personality" of the cancer. Knowing all the details about the cancer is essential to develop a treatment plan that makes the most sense for your specific situation.
Take the time to talk to your doctor about ALL of the information in your pathology report. Ask your doctor about any missing or incomplete information and any assumptions that are being made that could influence treatment decisions. Make sure HER2 testing was done and ask which type of test was performed. Many labs perform the IHC test as the standard test. A reading of 0 or 1+ is considered negative. A 3+ reading is considered positive. If your IHC result is 2+ (which is considered borderline), ask about having a FISH test done to more conclusively determine the cancer's HER2 status.
The Breastcancer.org Your Pathology Report pages offer more information about the information that should be in your report, as well as more about HER2 status and testing.
Data to guide HER2 testing of breast cancer patients in clinical practice remain scant but suggest substantial variation from current recommendations, according to a literature review.
The evidence suggested that two out of three eligible patients had no documentation of testing in claims records, one in five patients were either not tested or had no documentation of a positive test, and one in five test results might have been incorrect, investigators reported online in Cancer.
However, the paucity of useful information made the findings and conclusions tenuous at best. Even so, Kathryn A. Phillips, PhD, of the University of California San Francisco, and colleagues said the findings do not support a case for slowing the diffusion of technology in clinical practice.
"This case study illustrated how and what evidence might be improved to help guide decisions regarding emerging tests and associated therapies in cancer care," they concluded.
"It is crucial to build an evidence base that can support effective and efficient decision-making in regard to emerging technologies in clinical practice, considering their impact on clinical care and the healthcare system," they added.
The FDA has approved three tests for assessing HER2 status in breast tissue. The American Society of Clinical Oncology, College of American Pathologists, and National Comprehensive Cancer Network have recommended using one or more of the tests for determining and confirming HER2 status in patients with newly diagnosed breast cancer.
Despite the proven efficacy of trastuzumab (Herceptin) for treating HER2-positive breast cancer, uncertainty has persisted regarding the best approach to selecting patients for treatment, the authors said.
Moreover, concerns have arisen related to the accuracy and reliability of available tests.
In an effort to develop information to facilitate decision-making, Phillips and her co-authors reviewed literature related to use of HER2 testing in clinical practice.
They sought to address four specific issues:
The investigators identified few studies that provided information about the subject areas.
One study showed that about half of patients with metastatic breast cancer were tested for HER2 status, and another showed that 68% of patients had no documentation of testing in claims files. A third of patients treated with trastuzumab had no documentation of HER2 testing prior to the start of treatment.
The authors found only one study that described the approach to testing. That study showed that more than 90% of patients were evaluated by immunohistochemistry alone, fewer than 1% had only fluorescence in situ hybridization analysis, and 6% received both types of tests.
The review yielded no studies of direct comparisons involving community-based and central or reference-lab testing. However, results of one clinical trial showed a 20% rate of discordance between community and reference laboratories for patients enrolled from community-based oncology practices.
The authors identified one analysis of unpublished data regarding the appropriateness of trastuzumab therapy. It showed that 12% to 20% of patients who received the drug had either equivocal or negative HER2 test results.
Examination of 621 studies produced only four that assessed the cost-effectiveness of HER2 testing or trastuzumab therapy.
Two studies focused on therapy and assumed testing had been performed; one study assessed testing as a generic variable and did not examine different testing strategies. The fourth study evaluated seven potential testing strategies in cost-effectiveness models.
None of the studies yielded information the authors found useful for assessing the cost-effectiveness of HER2 testing in clinical practice.
"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."
Phillips disclosed relationships with the Blue Shield Foundation of California and the Aetna Foundation. Co-author Jennifer Haas disclosed relationships with the Blue Shield Foundation of California and with Pfizer.
Primary source: Cancer Source reference: Phillips KA. et al "Clinical practice patterns and cost effectiveness of human epidermal growth receptor 2 testing strategies in breast cancer patients" Cancer 2009; 115: DOI: 10.1002/cncr.24574.
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