Immunohistochemical methods for predicting cell of origin and survival in patients with diffuse large B-cell lymphoma treated with rituximab

Abstract

Purpose: Patients with diffuse large B-cell lymphoma (DLBCL) can be divided into prognostic groups based on the cell of origin of the tumor as determined by microarray analysis. Various immunohistochemical algorithms have been developed to replicate these microarray results and/or stratify patients according to survival. This study compares some of those algorithms and also proposes some modifications.

Patients and methods: Two-hundred and sixty-two cases of de novo DLBCL treated with rituximab and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP-like therapy were examined.

Results: The Choi algorithm and Hans algorithm had high concordance with the microarray results. Modifications of the Choi and Hans algorithms for ease of use still retained high concordance with the microarray results. Although the Nyman and Muris algorithms had high concordance with the microarray results, each had a low value for either sensitivity or specificity. The use of LMO2 alone showed the lowest concordance with the microarray results. A new algorithm (Tally) using a combination of antibodies, but without regard to the order of examination, showed the greatest concordance with microarray results. All of the algorithms divided patients into groups with significantly different overall and event-free survivals, but with different hazard ratios. With the exception of the Nyman algorithm, this survival prediction was independent of the International Prognostic Index. Although the Muris algorithm had prognostic significance, it misclassified a large number of cases with activated B-cell type DLBCL.

Conclusion: The Tally algorithm showed the best concordance with the microarray data while maintaining prognostic significance and ease of use.

Fig 1.

Immunohistochemical algorithms examined in this study. The cutoff for positivity is 30% of the tumor cells showing expression unless otherwise indicated (Choi and Muris algorithms). In the Tally algorithm, antibody results are not examined in a particular order. Two antigens of germinal center B cells and two antigens of activated B cells are examined. The immunophenotype with more positive antigens is determined. If an equal number of germinal center B-cell immunophenotype (GCB) and activated B-cell immunophenotype (ABC) antigens are positive, then LMO2 determines the phenotype. Choi*, modified Choi algorithm; Hans*, modified Hans algorithm.

Fig 2.

Overall survival of patients with diffuse large B-cell lymphoma according to immunophenotype by each algorithm. The number of patients (n) is listed next to the immunophenotype result, and n varies among the algorithms because of loss of tissue cores during staining. The probability that the two patient groups have equivalent survivals and the algorithm used is noted in the lower left corner of each graph. GCB, germinal center B-cell immunophenotype; ABC, activated B-cell immunophenotype.

Fig 3.

Event-free survival of patients with diffuse large B-cell lymphoma according to immunophenotype by each algorithm. The number of patients (n) is listed next to the immunophenotype result, and n varies among the algorithms as a result of loss of tissue cores during staining. The probability that the two patient groups have equivalent survivals and the algorithm used is noted in the lower left corner of each graph. GCB, germinal center B-cell immunophenotype; ABC, activated B-cell immunophenotype.

Fig A1.

Immunostains for BCL6 should have medium to strong nuclear positivity (A), without cytoplasmic staining. Immunostains for LMO2 should have strong nuclear positivity (B, C), but may have weak (B) or strong (C) cytoplasmic staining as well. Immunostains for LMO2 that have cytoplasmic staining without nuclear positivity (D) should be considered negative. All micrographs at ×400 magnification.