Prognostic immunophenotypic biomarker studies in diffuse large B cell lymphoma with special emphasis on rational determination of cut-off scores

A number of biomarkers, particularly proteins that contribute to prognosis in diffuse large B cell lymphoma (DLBCL), have been identified. However, translation into accepted standards to predict survival has not yet been accomplished, primarily due to contradictory reports in the literature resulting from, among other factors, arbitrary methodologies used to set cut-off values for determining positivity. Some of these problems might be resolved by application of rational statistical methods for determination of cut-off scores. Herein, we critically address issues on in situ phenotypic prognostic tumor-related biomarkers in DLBCL with a particular and practical emphasis on tools for cut-off level determination, especially receiver operating characteristic curve analysis. Moreover, we candidly illustrate the application of these tools for efficient disease-specific survival prognostication on a tissue microarray collective of 240 primary DLBCL using the common prognostic biomarkers Bcl-2, Bcl-6, CD10, FOXP1, MUM1, and Cyclin E. Comparison of the results relative to disease-specific survival unequivocally showed the superior discriminatory power of the cut-off levels calculated by receiver operating curves and the Youden's index, compared to arbitrary cut-off values from the literature, advocating fundamental application of rational methods for determination of clinically relevant prognostic biomarkers' cut-off scores.