Distribution and clinical impact of molecular subtypes with Dark Zone signature of DLBCL in a Japanese real-world study.

The distribution and clinical impact of cell-of-origin (COO) subtypes of diffuse large B-cell lymphoma (DLBCL) outside Western countries remain unknown. Recent literature also suggests that there is an additional COO subtype associated with the germinal center dark zone, that warrants wider validation to generalize clinical relevance. Here, we assembled a cohort of Japanese patients with untreated DLBCL and determined the refined COO subtypes, that include the dark zone signature (DZsig), using the NanoString DLBCL90 assay. To compare the distribution and clinical characteristics of the molecular subtypes, we used a dataset from the cohort of BC Cancer (BCC) (n = 804). Of the 1050 patients where DLBCL90 assay was successfully performed in our cohort, 35%, 45%, and 6% of patients were identified to be germinal center B-cell-like (GCB)-DLBCL, activated B-cell-like (ABC)-DLBCL, and DZsigpos-DLBCL, respectively, with the highest prevalence of ABC-DLBCL differing significantly from that of BCC (P < 0.001). GCB-DLBCL, ABC-DLBCL, and DZsigpos-DLBCL were associated with two-year overall survival rates of 88%, 75%, and 66%, respectively (P < 0.0001), with patients of the DZsigpos-DLBCL having the poorest prognosis. In contrast, GCB-DLBCL without DZsig showed excellent outcomes following rituximab-containing immunochemotherapy. DZsigpos-DLBCL was associated with the significant enrichment of tumors with CD10 expression, concurrent MYC/BCL2 expression, and depletion of microenvironmental components (all P < 0.05). These results provide evidence of the distinct distribution of clinically relevant molecular subtypes in Japanese DLBCL and that refined COO, as measured by the DLBCL90 assay, is a robust prognostic biomarker that is consistent across geographical areas.