LymphGen Classification of Diffuse Large B-Cell Lymphoma in a Cohort of Adolescent and Young Adult (AYA) Patients

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common form of NHL. It most commonly affects older adults, and clinical and genomic studies in the adolescent and young adult population (AYA) are still evolving. DLBCL has classically been categorized by germinal center (GCB) or non-germinal center (non-GCB) subtypes, based on cell of origin. Next-generation sequencing platforms have identified unique genetic markers and further classified DLBCL into molecular subtypes (Schmidt et al NEJM 2018). The LymphGen algorithm converts DLBCL NGS data into 7 molecular subtypes which may provide prognostic value and potential targets for therapy (Wright et al, Cancer Cell 2020). We report the first classification of molecular subtypes of diffuse large B-cell lymphoma (DLBCL) among adolescent and young adult (AYA) patients.

Methods: We screened the MSKCC-IMPACT database for clinical DLBCL samples submitted for NGS evaluation from AYA patients (diagnosed at ages 15-39 years of age) at our institution. 36 reports with at least 1 genetic abnormality excluding PMBL were extracted from June 2015- October 2021. The corresponding NGS data including copy number alterations and mutations were reformatted to run the LymphGen Algorithm (Zhu et al, Modern Pathology 2022 pg.1056). BCL2, BCL6, and MYC translocation status were obtained from clinical cytogenetic reports and cell of origin by immunohistochemistry. Age, gender, IPI risk score and clinical outcomes were also recorded.

Results: We found 36 patients in our search ranging from 19.1 years to 38.9 years old, with the median age being 29 years (Table 1). Of these, 64% were male, and 36% female. A majority of our NGS results were collected at time of diagnosis (78%) with the remaining (22%) taken after relapse. 16 of 36 (44.4%) cases were assigned to one of the six categories (EZB: 25.0%, ST2:13.9%, BN2:5.6%). No cases were assigned to MCD, N1, or A53 subtypes. 55.6% were classified as other. Within the assigned 16 cases, 62.5% of cases were called with high confidence (Core group, >90% probability), and one-third were called with lower confidence (Extended group, 50-90% probability). Correlation of genetic subtypes and cell of origin was similar to published data, with most (78%) EZB and (60%) ST2 cases concentrated in GCB, and BN2 being equally distributed between GCB and non-GCB. By age, BN2 and EZB cases tended to be older, with median age at 36.2 and 34.8 respectively, and ST2 being youngest with a median of 27.7 years. B2M was the most frequently mutated gene, with 33% of our cohort harboring at least 1 mutation, followed by KMT2D (Table 2) which were both enriched in the BN2 subtype. The frequency of mutated genes was higher in ST2 with 14 genes, followed by EZB with 10, and BN2 with 6. TP53, MYD88 and NOTCH1 mutations which are main contributors to the A53, MCD and N1 subtypes respectively were infrequent or absent in this group, suggesting that these somatic mutations may be acquired with increasing age. These subtypes have also been associated with the Activated B-Cell Subtype (ABC), which is known to become more prevalent with age. Comparing IHC and FISH results, all our BN2 samples were positive for BCL6 rearrangement while 71% of EZB samples had the BCL2 translocation, consistent with prior studies.

Conclusions: Our results show the feasibility of genetic classification for DLBCL by LymphGen on a clinical NGS panel in this understudied age group. Application of clinical NGS panels for targeted treatment decisions, such as the addition of ibrutinib to RCHOP (Wilson et al, Cancer Cell 2021) for MCD and N1 tumors, is an ongoing area of investigation. Notably, the distribution of subtypes was different than expected, with only 3 subtypes identified in our sample set. This observation requires further validation with a larger cohort with older and younger patients. Evaluation of these results in a larger data set, as well as comparisons to older patients with DLBCL, may identify unique mutations and allow for targeted clinical trials for this age group.

Zhu:Leica Biosystems: Consultancy. Joffe:Abbvie: Honoraria; Beigene: Honoraria. Batlevi:Bristol-Myers Squibb: Other: Ownership / Equity Interests; Provision of Services; Epizyme: Research Funding; Dava Oncology: Other: Provision of Services; Janssen: Research Funding; Autolus: Research Funding; Bayer: Research Funding; ADC Therapeutics: Other: Provision of Services; Novartis: Research Funding; Roche/Genentech: Research Funding; Xynomic: Research Funding; GLG Pharma: Consultancy; Juno/Celgene: Consultancy; Kite Pharma: Consultancy; Life Sciences: Consultancy; Seattle Genetics: Consultancy. Matasar:IMV Therapeutics: Consultancy, Honoraria; Rocket Medical: Consultancy, Research Funding; Pharmacyclics: Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Teva: Consultancy; Karyopharm: Consultancy; Merck: Consultancy, Current equity holder in private company; Juno Therapeutics: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; ImmunoVaccine Technologies: Honoraria, Research Funding; Daiichi Sankyo: Consultancy; F. Hoffmann-La Roche Ltd.: Consultancy, Honoraria, Research Funding; Genentech, Inc.: Consultancy, Honoraria, Research Funding; IGM Biosciences: Research Funding; ADC Therapeutics: Consultancy, Honoraria; Janssen: Honoraria, Research Funding; GlaxoSmithKline: Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; AstraZeneca: Consultancy; TG Therapeutics: Consultancy. Dogan:Incyte: Consultancy; EUSA Pharma: Consultancy; Peer View: Honoraria; Takeda: Other: Research Funding; Roche: Other: Research Funding; Physicians' Education Resource: Consultancy, Honoraria; Seattle Genetics: Consultancy; Loxo: Consultancy. Zelenetz:MBS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Pharmacyclics/Abbvie: Consultancy, Honoraria; Beigene: Consultancy, Honoraria, Research Funding; Gilead/Kite Pharma: Consultancy, Honoraria; Genentech/Roche: Consultancy, Honoraria, Research Funding; Juno Pharmaceuticals: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Salles:Roche/Genentech, Gilead Sciences, Janssen, Celgene, Novartis, MorphoSys AG, Epizyme, Alimera Sciences, Genmab, Debiopharm Group, Velosbio, Bristol-Myers Squibb, BeiGene, Incyte, Miltenyi Biotec, Ipsen, Kite, a Gilead Company, Loxo, Rapt: Consultancy; AbbVie, BeiGene, Bristol Myers Squibb, Celgene, Debiopharm, Epizyme, Genentech/Roche, Genmab, Incyte, Kite, a Gilead Company, Miltenyi, MorphoSys, Takeda, and VelosBio: Membership on an entity's Board of Directors or advisory committees; Roche/Genentech, Janssen, Celgene, Gilead Sciences, Novartis, AbbVie, MorphoSys AG, Amgen, Bayer, Epizyme, Regeneron, Kite, a Gilead Company: Honoraria.