Clonality relatedness and molecular characteristics of Richter transformation

Abstract

Objective: To investigate the clinical, genetic, and clonality related aspects of individuals with Richter transformation (RT) . Methods: From January 2019 to December 2021, 18 RT patients with diagnoses at the First Affiliated Hospital of Nanjing Medical University (Pukou CLL center) were retrospectively examined. The immunoglobin heavy variable (IGHV) gene usage and IGHV-D-J rearrangement pattern of diagnosed CLL/SLL and transformed diffuse large B-cell lymphoma (DLBCL) were compared to determine the clonality relatedness. To investigate the risk factors of RT, Clinical and laboratory data from patients with newly diagnosed CLL/SLL and transformed DLBCL were gathered. Results: The median age of RT was 56.5 (41-75) years old. 17 patients transformed to DLBCL and 1 transformed to Hodgkin lymphoma (HL) . Of 17 individuals who had DLBCL transformation, 15 had CLL/SLL-related clonality and 2 had unrelated clonality. Next-generation sequencing (NGS) analysis of 11 paired initially diagnosed treatment-naive CLL/SLL and RT DLBCL found that EGR2、TP53 and NOTCH1 were among the most frequently mutated genes both in treatment-naive CLL/SLL and in RT DLBCL. In several cases, specific mutations were gained or lost throughout RT, indicating clonal evolution. Among 10 patients before exposure to BTK inhibitors before RT, four patients acquired BTK mutation. The aforementioned mutations should be considered high-risk variables for transformation; in addition, TP53 and EGR2 mutations could be linked to a poor prognosis following RT in patients receiving a cocktail of new medicines. Conclusion: Most RT DLBCL patients in our center are clonality related (15/17, 88.2% ) and we recommend all qualified centers to evaluate clonality relatedness of RT DLBCL patients. There was some variability in the mutational landscape between DLBCL that had undergone a transformation and initially diagnosed, treatment-naive CLL/SLL. The underlying molecular mechanism of RT needs more research.