Prognostic Significance of Cell of Origin Subclassification in Diffuse Large B Cell Lymphoma

Diffuse large B cell lymphoma (DLBCL) is a heterogeneous disease that has been divided into three different prognostic subgroups: Germinal Center B cell-like (GC), Activated B cell-like (ABC) and type 3 according to gene expression profile using cDNA. Immunohistochemistry (IHC) has been used as surrogate to identify these cell-of-origin subgroups. Data about the prognostic value of IHC has been conflicting.

In this retrospective study, we reviewed the charts of 252 patients diagnosed with DLBCL at Henry Ford Hospital from 1999 to 2012. We excluded patients with HIV, transformed lymphomas and unavailable samples. Data was collected on a total of 157 patients. The following data was gathered: age, sex, race, IPI score, disease stage, hemoglobin, white blood and platelet counts, best response achieved and dates of treatment start, relapse, death or last follow up. Tissue microarray slides with the following IHC stains (CD10, MUM1, Bcl6) were prepared and reviewed when needed. Using Hans Algorithm, samples were divided into two major groups (GC-like and non-GC-like). 3-year progression free and overall survivals were compared between all subgroups using a log-rank test. Continuous variables were reported as median and range, and compared using Wilcoxon rank-sum tests. Categorical variables were reported as median and range, and compared using Chi-square tests. Statistical significance was set at p<0. 05.

Eighty patients (51%) were classified as GC-like, and 77 patients (49%) as non-GC-like. GC-like subgroup had a significantly longer 3-year progression free survival (90% vs 74%, P=0. 024), as compared with the non-GC-like subgroup. There was a trend toward longer overall survival but it didn't reach statistical significance (74% vs 67%, P=0. 161). For all patients, IPI stands as a strong prognostic index with 3-year overall survival of (85% and 46%, P=<. 001) in patients with low IPI (0 to 2) and high IPI (3 to 5) respectively. Interestingly, in patients with low IPI, cell of origin stands as a prognostic factor with 3-year progression free survival of (96% and 81%, P=0. 032) in GC-like and non-GC-like groups respectively. While in patients with high IPI, there was no significant difference in progression free survival in cell-of-origin subgroups.

Cell of origin subclassification as determined by IHC surrogate markers predict for better progression free survival in GC-like subgroup but not for overall survival. While this prognostic value was maintained in patients with low IPI, there was no prognostic significance in patients with high IPI. IPI is still a valuable prognostic tool in patients with DLBCL.

No relevant conflicts of interest to declare.