RELAPSE CHARACTERIZATION IN DIFFUSE LARGE B CELL LYMPHOMA PATIENTS UNDERGOING COMMERCIAL CAR‐T CELL THERAPY: EXPERIENCE FROM A SINGLE CENTRE

CAR-T cell therapy is approved for the treatment of adults with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL). However, 40-60% patients relapse after and characterization has been poorly reported. To describe characteristics in biopsy samples DLBCL receiving our center. All consecutive diagnosed R/R who were infused commercial cells from June 2019 to December 2020 included. expansion PB was monitored by multiparameter flow cytometry (FC) through detection labeled CD19 T (Human Protein®). PET-CT scanner evaluation performed on days +30, +90 +180. In cases where detected progression indeterminate response, core-needle accessible lesions performed. Study included: histological analysis; FC immune phenotyping including presence exhausted CD3+ populations (LAG3, TIM3, PD1). DNA purified using GeneRead FFPE Kit (Qiagen). Mutations (exon2-5) analyzed Sanger sequencing. 30 treated: 21 axi-cel 9 tisa-cel. Median age at infusion 57 years (r: 22-79); 16 (53%) female. follow up-was 9.5 months 3-18). PFS 6 42% OS 72%. 29 (97%). Complete overall response rate day (CR ORR) 39% 75%, respectively (28 evaluable patients), 41% 55% 100, (27 patients). At 180, 10 out 14 (38.5%) showed CR. A total 15 experienced progression. Biopsy (66%) (Table 1). Relapsed confirmed all except one whom sample insufficient. Three CD19+ IHQ pre-infusion CD19- relapse. patient that did not expand 2 infusions 60% presented biopsy. TME (tumor microenvironment) TCD3+ lymphocytes >20% 80% no had <5%. tumor sample, failed identify cellularity 37% patients; rest samples, percentage TCD3 an average (range 64-84). study revealed mutation (p.V279L) a series lymphomas anti-CD19 treatment, present but only tissue. loss mutations are possible mechanisms. Exhausted abundant TME, which would support its relevant role preventing good function carts situ. More complex biopsies analyses necessary better understand No conflicts interests pertinent abstract.