SELDI-TOF MS serum protein profiles in breast cancer: assessment of robustness and validity

There is an urgent need for new serum markers that can be applied in e.g. the early detection of breast cancer. Following detection of new, potential biomarkers, such as those reported by Vlahou et al. (Clin Breast Cancer 2003;4:230-239) and Laronga et al. (Dis Markers 2003;19:229-238), assessment of both their robustness and validity is essential to confirm their clinical applicability. We therefore aimed to determine robustness and validity of biomarkers reported by the authors mentioned, by analysis of an independent sample set (breast cancer: n=47, normal women: n=45) in our laboratory, according to the methods described by both authors. Although all markers for the differentiation between breast cancer patients and normal women, discovered in the study of Vlahou et al., were recovered in our validation data set, none had sufficient performance to be applied as a classifier. The markers discovered by Laronga et al. in the differentiation between lymph node positive and -negative breast cancer patients were in part recovered from our validation data set, but were also not applicable as a classifier. In conclusion, although (part of) the proteins discovered and designated as markers by either author could be detected, their validity as biomarkers could not be confirmed by the current study. This finding stresses that, when reporting on a potential biomarker, confirmation of both robustness and validity is essential in obtaining its true clinical applicability.