MYC Gene Simple Hit Is a Strong Independent Predictive Factor of Survival in Diffuse Large B-Cell Lymphomas in Contrast to MYC Double-Hit Gene Alterations: A Study by the Groupe d'Etude Des Lymphomes De l'Adulte

Diffuse large B-cell lymphomas (DLBCL) represent a heterogeneous group of tumors with variable clinical, morphological, and molecular features. The International Prognostic index (IPI) imperfectly stratifies patients and does not reflect the molecular heterogeneity of the disease. New tools for stratifying DLBCL patients in routine practice are needed.

The aim of the study was to analyse the prognostic relevance of CMYC, BCL2 and BCL6 rearrangements and the correlation with CMYC protein expression in a large series of 776 CD20+ de novo DLBCL treated with R-chemotherapy included in the Groupe d'Etude des Lymphomes de l'Adulte (GELA) trials.

Patients with de novo CD20+ DLBCL were enrolled in the randomized LNH-03 GELA trials (LNH-03-1B, -2B, -3B, 39B, -6B, 7B-, 5B). Seven hundred seventy six patients treated with anthracyclin based chemotherapy (R-CHOP/R-miniCHOP=483 or R-ACVBP=293) were eligible for the study. Tumor samples were analyzed by Fluorescence in situ hybridization (FISH) using split signal FISH DNA probes for BCL2/18q21, BCL6/8q27 and CMYC/8q24 and were immunostained for the expression of CMYC protein on tissue microarrays.

Five hundred seventy six DLBCL samples were evaluable for MYC rearrangement. Rearrangement of MYC, BCL2, and BCL6 genes were observed in 9.2% (53/576), 15.9 % (82/515), and 23.8% (129/541) of DLBCL, respectively. Fifteen cases showed both BCL2/BCL6 gene rearrangement. MYC rearranged cases (MYC-R+) included 21 MYC simple-hit (MYC-SH) and 32 MYC double or triple hit with concurrent BCL2 and/or BCL6 rearrangement (MYC-DH) DLBCL. There were 33 male and 20 women, with a median age of 62 years [range, 18–93], and 5 were stage I-II and 48 stage III-IV according to Ann Arbor. The common histological feature of the MYC-SH cases was an increased mitotic rate but a starry sky pattern with tingible body macrophages was observed only in 2 cases. MYC protein expression was found positive in 30/45 (66%) evaluable MYC-R+ cases using a cut off of ≥70% of positive tumor cells.

In univariate analysis, IPI had a significant impact on OS (P< .0001). BCL2, BCL6 gene alterations did not significantly predict survival (PFS, EFS, OS). MYC-R+ breakpoint was associated with a shorter 5-year OS rate (57.7% vs 73.7%, P= 0.01) which remained significant in the R-CHOP treated group of patients (P=0.04). When separating MYC-SH and MYC-DH DLBCL, MYC-SH maintained a significant impact on survival in the global population as well as in the R-CHOP group of patients. By contrast, MYC-DH had no significant impact on OS in the global population and in the R-CHOP group of patients. In multivariate analysis, the prognostic impact of the IPI, MYC-R+ and MYC-SH breakpoint remained significant.

This is the first large extensive study on the prognosis impact of MYC rearrangement in controlled trial of DLBCL patients treated with R-chemotherapy. MYC-SH had an adverse prognostic effect on survival. Interestingly, in contrast to previous published studies, this impact was not maintained in the MYC-DH DLBCL suggesting different biological response to treatment between the two groups. Immunostaining for MYC protein was not efficient to detect MYC rearranged cases. FISH for MYC, BCL2 and BCL6 should be performed systematically to differentiate MYC-SH and MYC-DH in future clinical trials.

No relevant conflicts of interest to declare.