Cell-of-origin classification using the Hans and Lymph2Cx algorithms in primary cutaneous large B-cell lymphomas

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) and primary cutaneous follicle center lymphoma with a diffuse population of large cells (PCFCL-LC) are both primary cutaneous B-cell lymphomas with large-cell morphology (CLBCL) but with different clinical characteristics and behavior. In systemic diffuse large B-cell lymphoma, not otherwise specified (DLBCL-NOS), gene-expression profiling (GEP) revealed two molecular subgroups based on their cell-of-origin (COO) with prognostic significance: the germinal center B-cell-like (GCB) subtype and the activated B-cell-like (ABC) subtype. This study investigated whether COO classification is a useful tool for classification of CLBCL. For this retrospective study, 51 patients with PCDLBCL-LT and 15 patients with PCFCL-LC were analyzed for their COO according to the immunohistochemistry-based Hans algorithm and the NanoString GEP-based Lymph2Cx algorithm. In PCFCL-LC, all cases (100%) classified as GCB by both Hans and Lymph2Cx. In contrast, COO classification in PCDLBCL-LT was heterogeneous. Using Hans, 75% of the PCDLBCL-LT patients classified as non-GCB and 25% as GCB, while Lymph2Cx classified only 18% as ABC, 43% as unclassified/intermediate, and 39% as GCB. These COO subgroups did not differ in the expression of BCL2 and IgM, mutations in MYD88 and/or CD79B, loss of CDKN2A, or survival. In conclusion, PCFCL-LC uniformly classified as GCB, while PCDLBCL-LT classified along the COO spectrum of DLBCL-NOS using the Hans and Lymph2Cx algorithms. In contrast to DLBCL-NOS, the clinical relevance of COO classification in CLBCL using these algorithms has limitations and cannot be used as an alternative for the current multiparameter approach in differentiation of PCDLBCL-LT and PCFCL-LC.

Indirect Comparison of Tisagenlecleucel and Historical Treatments for Relapsed/Refractory Diffuse Large B-cell Lymphoma

No head-to-head trials have compared the efficacy of tisagenlecleucel versus historical treatments for adults with relapsed or refractory diffuse large B-cell lymphoma (r/r DLBCL). This study indirectly compared the overall survival (OS) and overall response rate (ORR) associated with tisagenlecleucel, using data from the JULIET study (NCT02445248), versus historical treatments assessed in the CORAL study follow-up population. To assess treatment effects in the treated (full analysis set [FAS]) and enrolled (intent-to-treat [ITT]) study populations, the JULIET FAS vs. the CORAL follow-up FAS and JULIET ITT vs. CORAL follow-up ITT populations were separately compared. Propensity score weighting using standardized mortality ratio weight (SMRW) and fine stratification weight (FSW) was used to compare OS and ORR, adjusting for baseline confounders. The results indicated that tisagenlecleucel was associated with a lower hazard of death among the FAS (adjusted hazard ratio [95% CI], both FSW and SMRW: 0.44 [0.32, 0.59]) and ITT populations (FSW: 0.60 [0.44, 0.77], SMRW: 0.57 [0.44, 0.73]; all p<0.001). Median OS was 12.48 months (JULIET) vs. 4.34-4.40 months (CORAL) for the FAS, and 8.25 (JULIET) vs. 4.04-4.86 (CORAL) for the ITT populations. Tisagenlecleucel was associated with a significantly higher ORR compared to historical treatments among the FAS (adjusted response rate difference [95% CI], both FSW and SMRW: 36% [22%, 0.48%]; p<0.001) and among the ITT populations after SMRW adjustment (11% [0%, 22%]; p=0.043). This analysis supports that improved response and OS are achieved in r/r DLBCL patients treated with tisagenlecleucel when compared to those treated with alternative historical treatments.

Follicular lymphoma grade 3B and diffuse large B-cell lymphoma present a histopathological and molecular continuum lacking features of progression/transformation

The sole distinguishing feature of follicular lymphoma grade 3B and diffuse large B-cell lymphoma is the growth pattern assessed by histopathology analysis. Diffuse growth defines diffuse large B-cell lymphoma but the clinical relevance of this finding when occurring in follicular lymphoma grade 3B is uncertain. To address this question, individual and coexisting follicular lymphoma grade 3B and diffuse large B-cell lymphoma were separated and analyzed for immunophenotype and molecular genetic features by fluorescence in situ hybridization, targeted sequencing and gene expression profiling. Clinical features of follicular lymphoma grade 3B with and without coexisting diffuse large B-cell lymphoma were studied in homogeneously treated patients from a prospective randomized trial. Follicular lymphoma grade 3B and diffuse large B-cell lymphoma frequently show intermediate growth pattern and/or occurred simultaneously in the same tissue at the time of initial diagnosis. When occurring simultaneously follicular lymphoma grade 3B and diffuse large B-cell lymphoma do not differ significantly in genetic aberrations or phenotype but distinct features in gene expression reflect divergent microenvironment. Follicular lymphoma grade 3B with and without coexisting diffuse large B-cell lymphoma do not differ in major clinical parameters such as international prognostic index, response to immunochemotherapy, progression or overall survival. Follicular lymphoma grade 3B and simultaneous diffuse large B-cell lymphoma are molecularly homogenous. Histological detection of diffuse large B-cell lymphoma is not associated with features of a more aggressive disease and does not reflect transformation or progression of follicular lymphoma Grade 3B.