Gene-Expression Assays for Breast Cancer Concur

A number of gene-expression assays have been developed that appear to be predictive for cancer patients, especially breast cancer patients, but tests show very little overlap in the genes involved and it is not known how distinct these different assays might be.

Activity patterns in the genes of individual tumors can be predictors of how likely the tumors are to be invasive, how well they might respond to different treatments, and how likely they are to recur or spread. To compare the individual predictions made by different genomic tests, Dr. Charles M. Perou, assistant professor of genetics and pathology at the University of North Carolina (UNC) School of Medicine (Chapel Hill, NC, USA), and colleagues studied the concordance of five different predictors that were all applied to a single data set of 295 tumor samples for which patient survival data were available.

Writing in the August 10, 2006, issue of the New England Journal of Medicine, the researchers note that four predictors showed significant agreement in their outcome predictions on individual breast cancer patients, despite having little gene overlap. Of the three predictors showing the greatest concordance, two were the main assays that are commercially available and being used to guide clinical trials.

If one assay said this patient was going to do poorly, then so did the other two, said Dr. Perou, noting that although two commercial assays overlapped by only one gene, they were in 80% agreement with each other. This is good news for breast cancer patients. It means that different groups have independently arrived at tests which agree with each other and that they all do add information not provided by existing clinical tests.

Several of the predictors in this study appear to predict the likelihood of breast cancer recurrence in various populations of women with node-negative disease. Such information would be useful for identifying women who are unlikely to experience recurrence and, thus, probably unlikely to benefit from chemotherapy.



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