Molecular and Clinical Analysis of Large B-Cell Lymphomas with MYC gene Involvement: Impact of the Co-Occurrence of TP53 Deletion

Background: Diffuse Large B-cell lymphoma (DLBCL) is a heterogeneous disease, with different clinical behaviors and biological characteristics. High-grade B-cell lymphomas (HGBL) with MYC and BCL2 and/or BCL6 rearrangement represent a separate entity with lower response to R-CHOP like regimens and poorer outcome. Additional molecular risk stratification of DLBCL/HGBL carrying MYC alterations could provide further prognostic information for an optimal choice of therapy. Major issues affecting risk stratification are characterization of MYC translocation partners, presence of TP53 gene alterations and determination of Cell of Origin (COO).

Aim: to provide preliminary data on additional molecular risk factors in patients with DLBCL/HGBL with MYC alterations and treated with R-CHOP-like regimens with curative intent. Cytogenetic and molecular findings will be correlated with clinical features and treatment outcome.

Methods: this is a retrospective multicentric study on DLBCL/HGBL patients with MYC gene involvement (MYC rearrangement and/or MYC anomalies identified by Fluorescent In Situ Hybridization, FISH). The following analyses were performed: a) immunohistochemical staining b) FISH to determine MYC, BCL2 and BCL6 rearrangements, MYC partner gene, MYC copy number and TP53 deletion, c) Targeted Next Generation Sequencing (NGS) to identify the unknown gene partner in non-immunoglobulin (IG)/MYC rearrangements and additional molecular alterations d) GEP Study to determine COO. Biological findings were correlated with baseline clinical data and response to therapy/survival.

Results: 42 patients were included in the study. All patients received first line treatment with R-CHOP like regimens. Median follow-up was 36 months. Median age was 65 years; 15/42 (36%) patients were low/intermediate IPI and 26/42 (62%) were intermediate-high/high IPI risk (1/42 data not available).

MYC increased copy number was detected in 8/42 (19%) patients, whereas MYC rearrangement (MYC-r) in 34/42 (81%). Of the MYC-r patients, 31/34 patients had sufficient material for subsequent analyses. MYC-r with an IG gene was observed in 19/31 (61%) patients. BCL2 and BCL6 rearrangements were reported in 20/39 (51%) and 14/39 (36%) cases, respectively. The co-occurrence of MYC and BCL2 rearrangement was detected in 12/31 (39%) patients, MYC and BCL6 in 6/31 (19%) patients and 4/31 (13%) patients were positive to all three genes. A TP53 deletion was present in 7/40 (18%) patients for whom the analysis was available.

COO was Germinal Centre B-Cell (GCB) subtype in 31/40 (78%) patients, Activated B-Cell (ABC) in 6/40 (15%) and unclassified in 3/40 (7%).

Three-year overall survival (OS) rate was 52% in all patients with MYC-r and 75% in patients with MYC gain (p=0.19). As expected, patients with MYC and BCL2 and/or BCL6 rearrangements showed a trend to worse OS (3-years OS rate 46%) as compared with patients with MYC-r only or with MYC gain (3-year OS rate 75% in both groups, p= 0.39). Patients with MYC-r and TP53 deletion showed a significant inferior OS (3-year OS 20%) as compared to patients without TP53 deletion and with MYC-r (3-year OS 59%) or MYC gain (3 year OS 75%) (p = 0.047).

Most prevalent pathogenic variants detected by NGS (i.e detected in >15% patients) were TP53 (33%), CREBBP (31%), MYC (31%), BCL2 (19%), TNFRS14 (19%), CIC (17%), EZH2 (17%) and NF1 (17%). Updated data and clinical correlation will be presented at the meeting.

Conclusion: With the limitations of the small sample size and retrospective nature of the study, our findings underline the adverse prognostic impact of TP53 deletion on OS in a cohort of high-risk large B cell lymphoma (LBCL) patients harboring MYC alterations (structural and/or numerical). The adverse clinical impact of the co-occurrence of MYC and/or BCL2/BCL6 rearrangements was confirmed. Evaluation of TP53 status should be included in standard diagnostic work-up of DLBCL/HGBL to further refine the prognosis. Identifying these high risk patients could potentially help to tailor treatments, for example considering novel immunotherapies earlier in the disease course in dedicated clinical studies. NGS may provide further insights. A full integration of clinical and biological data could ultimately allow better stratification of LBCL patients.

This study was funded by FPRC 5xmille 2017 MUR (INTERONC project) and FPRC 5xmille Ministero della Salute 2019 IDEE

Botto:TAKEDA: Speakers Bureau. Vitolo:AbbVie, Incyte, Janssen, Regeneron, Roche, Servier: Other: Lecture Fees; AbbVie, Bayer, Genmab, Gilead, Novartis: Membership on an entity's Board of Directors or advisory committees.