ABC, GCB, and Double-Hit Diffuse Large B-Cell Lymphoma: Does Subtype Make a Difference in Therapy Selection?

Personalized therapy for the treatment of patients with cancer is rapidly approaching and is an achievable goal in the near future. A substantial number of novel targets have been developed into therapeutic agents. There is a substantial variability to antitumor activity by novel therapeutics because of the unique heterogeneity and biology that exists both between and within lymphoma subtypes. Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL). Approximately 40% of patients have refractory disease or disease that will relapse after an initial response, and the majority of patients with relapsed DLBCL will succumb to the disease. There are two major biologically distinct molecular subtypes of DLBCL: germinal center B-cell (GCB) and activated B-cell (ABC). ABC DLBCL is associated with substantially worse outcomes when treated with standard chemoimmunotherapy. In addition to GCB and ABC subtypes, double-hit lymphomas (approximately 5% to 10% of patients) and double-expressor lymphomas, which overexpress MYC and BCL2 protein, are aggressive DLBCLs and are also associated with a poor prognosis. Double-hit lymphomas have concurrent chromosomal rearrangements of MYC plus BCL2 (or less likely, BCL6). Advances in molecular characterization techniques and the development of novel agents targeting specific subtypes of DLBCL have provided a foundation for personalized therapy of DLBCL based on molecular subtype. A number of early clinical trials evaluating combinations of novel targeted agents with standard chemotherapy (R-CHOP) have been completed and have demonstrated the feasibility of this approach with encouraging efficacy. As such, molecular classification of DLBCL is not only important for prognostication, but moves to center stage for personalization of therapy for DLBCL.