Durable Response to Venetoclax Monotherapy in Richter's Syndrome: A Case Report and Review of Literature

In 2017, 20,110 people in the United States were diagnosed with chronic lymphocytic leukemia (CLL). Of these patients, 5-15% will ultimately undergo Richter's syndrome (RS), a transformation to a more aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL) type. Particularly when the transformation is clonally related, prognosis is poor in these individuals with a median survival of only 5 - 14 months. This is an area of unmet need, and as such, the benefits of novel approaches with targeted therapies should be explored. Our patient is a 70-year-old female who was diagnosed with CLL in 2010. In 2016, she presented to her general practitioner with new B symptoms and leukocytosis. Cytogenetics on peripheral blood was notable for known trisomy 12 (52.8% of cells) and new 17p deletion (93.4% of cells). She received five cycles of ofatumumab with complete resolution of systemic symptoms but mixed response on interim computed tomography (CT) scan with ensuing rise in her white blood cell (WBC) and lactic acid dehydrogenase (LDH). A positron emission tomography (PET) scan had disproportionate uptake in the porta hepatis lymph nodes and subsequent lymph node biopsy confirmed transformation. She was started on R-CHOP chemotherapy but tolerated it very poorly. She was transitioned to venetoclax monotherapy in April 2017 and achieved a partial response by CT and bone marrow biopsy. This has been maintained over the last 12 months allowing the patient to travel and maintain a high quality of life. While the pathogenesis to RS is poorly understood, there have been several studies to identify tumor genetic changes predisposing to transformation. Of the proposed factors, a review of the literature consistently suggests p53 tumor suppressor gene mutation and/or 17p deletion to be associated with RS. Venetoclax is a selective BCL-2 inhibitor that is now approved for CLL patients with 17p deletion. This case serves as an example encouraging the use and study of novel agents such as venetoclax alone or in combination with traditional regimens or other novel agents to mitigate the poor prognosis of 17p deletion associated RS. Further research, however, is required to clarify the pathogenesis of RS and identify optimal treatment strategies.