International Consensus Statement on Diagnosis, Evaluation, and Research of Richter Transformation: the ERIC Recommendations

• Investigation of RT tissue is required for appropriate diagnosis and to understand the pathobiology of this poor-risk lymphoma subtype.

• Due to the poor prognosis of RT with conventional chemoimmunotherapy, participation in clinical trials should be prioritized.

Richter transformation (RT) is defined as an aggressive lymphoma emerging in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL). Despite novel therapeutics developed in CLL, RT is associated with poor outcomes. In light of recent progress regarding the diagnostic procedures and therapeutic concepts of RT, an international group of experts, under the coordination of the European Research Initiative on CLL (ERIC), has developed consensus recommendations for clinical procedures and future research on this disease. Patients with RT typically present with a rapid clinical decline, worsening B-symptoms, elevated LDH, and/or rapidly enlarging lymphadenopathy. Workup should include a PET-CT for patients with suspected RT. An excisional biopsy should be taken from an accessible lesion, preferably with the highest FDG avidity, and analyzed for the presence of aggressive lymphoma. The molecular relationship to the original CLL clone(s) should be defined. As no effective standard treatment for RT exists, patients should be treated in a clinical trial. Response of both RT and CLL should be assessed at an early time point, and survival endpoints should be prioritized in trial design. We hope that these recommendations can help to harmonize clinical and translational research and improve outcomes for patients with RT.