To compare the individual predictions made by these different genomic tests, Perou and his colleagues at UNC and at The Netherlands Cancer Institute in Amsterdam, The Netherlands, 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 was available relapse-free survival and overall survival.
Writing in the Aug. 10 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," Perou said, noting that although the two commercial assays overlapped each other only by one gene, they were in 80 percent 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," Perou said.
For example, 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, potentially unlikely to benefit from chemotherapy.
"We find our results encouraging and interpret them to mean that although different gene sets are being used, they are each tracking a common set of biological characteristics that are present across different breast cancers and are making similar outcome predictions," Perou said.