Information about the use and accuracy of breast cancer tests is lacking, study finds

September 14, 2009

A new study finds that there is little information available about the use of new testing technologies and targeted therapies in breast cancer, specifically the anti-cancer drug trastuzumab (Herceptin). Published in the November 15, 2009 issue of Cancer, a peer-reviewed journal of the American Cancer Society, the review suggests that many breast cancer patients who may benefit from trastuzumab are not receiving it, and that some women receiving the drug have never been tested for the receptor it targets.

Standard care now dictates that women with early-stage 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.

Researchers at the UCSF Center for Translational and Policy Research on Personalized Medicine (TRANSPERS) and led by Kathryn A. Phillips, PhD, of the University of California-San Francisco, reviewed the medical literature to determine how HER2 testing is being used in routine clinical practice. The studies they found 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 may be incorrect.

The authors also found that studies looking at the economic issues associated with prescribing trastuzumab often did not explicitly consider the role of HER2 testing, which can have a substantial impact on the cost-effectiveness of the therapy.

Given the increasing use of targeted therapies like trastuzumab, proper testing will become more important to ensure that medications are directed only to the patients who will benefit from them.

"Our review of the literature suggests that there are important knowledge gaps regarding the real-world use of HER2 testing and trastuzumab," said Dr. Elena Elkin, a researcher at Memorial Sloan-Kettering Cancer Center in New York and one of the study's authors. "Filling these gaps may help optimize limited health care resources and improve care for with breast cancer," she added.

More information: "Clinical practice patterns and cost-effectiveness of HER2 testing strategies in breast cancer patients." Kathryn A. Phillips, Deborah A. Marshall, Jennifer S. Haas, Elena B. Elkin, Su-Ying Liang, Michael J. Hassett, Ilia Ferrusi, Jane E. Brock, and Stephanie L Van Bebber. Cancer; Published Online: September 14, 2009 (DOI: 10.1002/cncr.24574); Print Issue Date: November 15, 2009.

Source: American Cancer Society (news : web)

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gdpawel
Sep 14, 2009

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I've often wondered if the underlying science of Herceptin is sound. Unlike a test for the presence of receptors to a specific antigen, which only "implies" dependence upon that antigen, a functional assay actually assesses the direct or indirect effect of the drug upon the whole cell, whether it is a tumor cell or an endothelial cell. Her2 just happens to be one molecule which has been implicated in the process but there may be more.

If it were the only protein involved, then one would expect that Her2 expression would correlate with Herceptin activity 100% of the time but it actually does so only about 20% of the time. The functional assay doesn't just focus on Her2 or any one protein or mechanism. Whether it's Her2 alone (unlikely) or in combination with other proteins and other mechanical factors, the assay works by assessing the net effect of all those factors.

gdpawel
Sep 14, 2009

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Many of these drugs cry out for validated clinical biomarkers to help set dosage and select people likely to respond. And optimal and reproducible Her2 testing continues to evade the diagnositcs of the disease. Numerous other genes, tumor, and patient factors contribute to the risk of the cancer coming back and the effectiveness of chemotherapy for breast cancer.

It could be vastly more beneficial to measure the net effect of all processes (systems) instead of just individual molecular targets. The cell is a system, an integrated, interacting network of genes, proteins, and other cellular constituents that produce functions. One needs to analyze the systems' response to drug treatments, not just one or a few targets (pathways/mechanisms).
gdpawel
Sep 14, 2009

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There are many pathways/mechanisms to the altered cellular (forest) function, hence all the different "trees" which correlate in different situations. Improvement can be made by measuring what happens at the end (the effects on the forest), rather than the status of the individual trees.
E_L_Earnhardt
Sep 17, 2009

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Cyroablation works, but there is little profit in it! The drug industry will never outlive the shame!
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