FROM JOURNAL OF CLINICAL ONCOLOGY
In patients with diffuse large B-cell lymphoma (DLBCL) treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), the Lymph2Cx assay was able to separate the cohort into groups with significantly different outcomes based on cell of origin (COO), investigators reported online in the Journal of Clinical Oncology.
In pairwise multivariable analyses, COO was associated with outcomes that were independent of International Prognostic Index score (IPI) and MYC/BCL2 immunohistochemistry (IHC).
Gene expression profiling of DLBCL has provided classification into two distinct subtypes: germinal center B-cell–like (GCB) and activated B-cell–like (ABC) subtypes. Using the cell of origin classification can define subgroups with distinct biology ad pathogenesis, as well as identify patient groups with different outcomes after treatment. Improvements in technology have allowed for the use of formalin-fixed paraffin-embedded tissue (FFPET) biopsies for more reliable gene expression profiling.
“The size of the study cohort allowed exploration of the prognostic value of COO in comparison with other prognostic tools,” wrote Dr. David W. Scott of the British Columbia Cancer Agency, Vancouver, and his colleagues (J Clin Oncol. 2015 Aug 3. doi: 10.1200/JCO.2014.60.2383 ).“Although the IPI remains the most powerful tool for risk stratification, COO assignment provides additional prognostic information, particularly evident in the intermediate IPI score group,” the authors noted.
The consistency and reproducibility of COO assignment using the Lymph2Cx assay was evaluated in a large patient cohort treated with R-CHOP therapy, and the relationship between COO, MYC/BCL2 dual expression, and IPI score with respect to defining prognosis in patients with DLBCL was also investigated.
Reproducibility of COO assignment using the Lymph2Cx assay was tested using repeated sampling within tumor biopsies and changes in reagent lots, and concordance of COO calls across the two reagent lots was 100%.
The COO was then determined in 344 patients with de novo DLBCL who were treated with R-CHOP at a single center. MYC and BCL2 protein expression was assessed using immunohistochemistry on tissue microarrays, and the median follow-up of living patients was 6.5 years (range, 0.75-13.2 years).
COO was a prognostic biomarker in the patient cohort. Those with activated B-cell–like DLBCL had significantly inferior outcomes as compared to patients with germinal center B-cell–like DLBCL (log-rank P less than .001 for time to progression, progression-free survival, disease-specific survival, and overall survival).
When reviewing the relationship between COO, IPI score, and MYC/BCL2 IHC, pairwise multivariable analyses demonstrated that the prognostic impact of COO is independent of IPI score. The prognostic value added by COO was most notable when patients with intermediate IPI scores were evaluated (ABC vs. GCB: 5-year time to progression, 53% v 74%; log-rank P = .003).
Both COO and MYC/BCL2 IHC identified high-risk groups that were similar in size (32% vs. 31%) with comparable outcomes (5-year time to progression, 51% vs. 51%). In pairwise multivariable analyses that included COO and MYC/BCL2 IHC as variables, COO remained significant, thus showing that COO had prognostic power “beyond that conferred merely by enrichment of MYC-positive/BCL2-positive patient cases of the ABC subtype,” wrote the authors.
When COO, IPI, and MYC/BCL2 IHC were all included in multivariable analyses, COO remained significantly associated with time to progression and progression-free survival.
“We anticipate that over the next few years, with the emergence of agents with selective activity in ABC or GCB DLBCL, the determination of COO will become part of the foundation for optimal patient care,” the authors concluded.
