New Assay May Help Clinicians Identify Lymphoma Subtypes

Oncology healthcare providers may have a new assay to help better evaluate prognosis and target effective therapies for lymphoma patients, according to French researchers. They are reporting in The Journal of Molecular Diagnostics that the use of the reverse transcriptase, multiplex ligation-dependent probe amplification (RT-MLPA) assay can differentiate the two major subtypes of diffuse large B-cell lymphoma (DLBCL).

The researchers write that with the advent of targeted lymphoma therapies on the horizon, it is increasingly important to differentiate between germinal center B-cell-like (GCB) and activated B-cell-like (ABC) lymphoma because they differ in management and outcomes. Their analyses suggest that the RT-MLPA assay is as accurate as the current gold standard technology, and offers advantages such as simplicity, flexibility and a short turnaround time.

Lead study investigator Philippe Ruminy, PhD, who is with the Centre Henri Becquerel, Institute for Research and Innovation in Biomedicine at the University of Rouen, Rouen, France, said the differences in the progression of the disease and clinical outcomes can in part be explained by the heterogeneity of lymphoma. He said identifying which cases is GCB or ABC is paramount; however, Dr. Ruminy said these lymphomas are morphologically undistinguishable in routine diagnosis.

The array-based gene expression profiling (GEP), which is considered the gold standard for discriminating these tumors, remains poorly transposable to routine diagnosis, according to Dr. Ruminy.  In addition, he said the surrogate immunohistochemical (IHC) algorithms that have been proposed may not be as reliable as clinicians would like.

Dr. Ruminy and colleagues analyzed lymph node biopsies from 259 patients with de novo DLBCL, including 195 patients from the Centre Henri Becquerel and 64 from an external group. The investigators compared the RT-MLPA assay to the gold standard method of distinguishing the two lymphoma subtypes. In a training series of 50 randomly selected DLBCL cases, the new method classified 90% of the cases into the expected subtypes (20 GCB and 25 ABC); however, 10% were considered unclassifiable. In a second independent validation series, 93% of 65 samples were classified correctly with the RT-MLPA assay.

The investigators also showed that the RT-MLPA assay was sensitive for analyzing archived formalin-fixed, paraffin-embedded (FFPE) tissue samples. Comparison of samples from paired frozen and FFPE biopsies showed that the RT-MLPA assay correctly classified 89.3% of 28 cases. The researchers looked at survival in 135 treated lymphoma patients diagnosed between 2001 and 2011 in order to evaluate the prognostic value of the assay. They found that patients determined to have the ABC subtype by the RT-MLPA assay had significantly worse progression-free survival (PFS) and overall survival (OS) than those with the GCB subtype. They also found that expression of several individual genes (high LMO2, high BCL6, and low TNFRSF13B expression) within the MLPA signature was significantly associated with prognosis.

Dr. Ruminy said the RT-MLPA assay yields results within one day and requires reagents costing less than $5 per sample. He noted this approach could easily be implemented for routine use.