A Genomic Approach for High-Grade B Cell Lymphoma with MYC and BCL2 and / or BCL6 Rearrangements: Two Clusters Stood out on Next Generation Sequencing Results

Introduction

High-grade B cell lymphomas with double or triple hit rearrangement (HGBL DH/TH), which appeared on the 4th revised edition WHO classification of lymphoid neoplasms, are aggressive mature B-cell lymphomas with high-grade cytology (Burkitt-like, blastoid or DLBCL-like) that have a MYC (8q24) rearrangement in combination with a BCL2 (18q21) and / or a BCL6 (3q27) rearrangement. There are currently no treatment guidelines for this subtype, and the usual immunochemotherapy leads to few complete remissions. While the NGS technology has been used in diffuse large B cell lymphoma, there has been no specific study on additional genetic events which would predict the clinical outcome in HGBL DH/TH. Here, we report our preliminary results using a targeted DNA capture panel approach (NGS) to identify subgroups with different clinical outcomes among HGBL DH/TH.

Methods

We conducted a retrospective study on 44 patients diagnosed with DH or TH HGBL and treated at Centre Hospitalier Lyon Sud or Centre Léon Bérard starting in 2013. We collected the medical information regarding the treatment, time to response to treatment or relapse, progression free survival, and overall survival. They all benefited from a DNA-targeted NGS analysis covering 54 genes.

Results

The cohort included 20 females and 24 males, with a median age of 65 (31-87). Among them, 22 patients were MYC/ BCL2 DH (50%), 12 were MYC/ BCL6 DH (27,3%) and 10 were TH (22,7%). Eleven patients had B symptoms (25%). The Ann Arbor stage was high (III-IV) in 97.5%. The WHO Performance Status was low (0-1) for most of the patients (70%). The majority of them presented with an IPI above to 2 (82,5%) and an elevated LDH level (80%). The Ki67 index was above 70% (33/42) in 78,5% of the cases and above 90% (19/42) in nearly half of them.

The major finding of the NGS analysis was the identification of 2 groups based on the TP53/ CDKN2A_p14ARF mutational status. The CDKN2A locus encodes for 2 alternative open reading frames leading to 2 unrelated proteins p14ARF and p16INK4A. P14ARF is involved in the regulation of the TP53 pathway whereas p16INK4A is not. We therefor defined 2 groups : the first group included patients with either TP53 or CDKN2A_p14ARF-only alterations (group A, n=10) while the second group had no alteration in these two coding sequences (group B, n=34) although 12 patients had a CDKN2A_p16INK4A loss or mutation affecting both CDKN2A transcripts. Most of TP53 mutations were missense mutations mostly in TP53 DNA-binding domain and 2 cases appeared to be single hit mutations with an allele frequency below 50%. The patient with a p14ARF only mutation had a start codon mutation p.(M1*) with an allele frequency of 96% without CDKN2A copy number loss.

The median overall survival (OS) (Figure 1) was 6,2 months for group A, and 55,5 months for group B (p = 0,0076). The median follow-up time was 14 months (7,5 months in the group A, 18 in group B). Only 2 patients in group A survived and are still in complete remission, one was DH BCL6 and the other DH BCL2

Conclusion

Our preliminary results indicate a strong negative prognostic impact of either CDKN2A_p14ARF or TP53 gene alterations on the OS of HGBL DH/TH patients. The biological basis for the difference between groups would be in favour of the alteration of the p14ARF-TP53 tumor suppressive pathway as major contributor of chemoresistance. A more detailed analysis is on-going to further identify mutation profiles of double hit and triple hit lymphomas and compare our finding with existing data.

Our results confirm the more favourable outcome of DH BCL6 patients (data not shown), which is consistent with the 5 ^th revised OMS classification that removed that specific entity.

Our results also indicate that routine NGS analysis of HGBL DH/TH patients offers new perspectives for patient stratification. Regarding their survival, patients with TP53 pathway alterations should probably not be treated with the standard RCHOP chemo-immunotherapy. Instead, a more intensive immunochemotherapy regimen or novel strategies such as first-line bispecific antibodies or CARTCells might be considered.