Gene-Expression Signatures in Breast Cancer

The study by van de Vijver et al. is of considerable interest with respect to the biology of breast cancer. However, from the point of view of the individual patient and her physician, the sensitivity and specificity of prognostic profiles are more important than odds ratios. It is possible to calculate these factors in part from the results. For example, for "all new patients in the consecutive series" (180 patients, listed in Table 2 of the article), the sensitivity and specificity of the poor prognostic signature are 0.93 (95 percent confidence interval, 0.81 to 0.98) and 0.53 (95 percent confidence interval, 0.45 to 0.61), respectively. If a hypothetical treatment were administered on this basis, nearly two thirds of the patients with a poor prognostic signature (65 of 104 patients) would be overtreated. Thus, the reported genetic signatures do not seem to be much sharper weapons for daily practice than other, easier-to-obtain prognostic indicators