Additional Study Information: The purpose of this study is to determine the effectiveness of the study treatment- bendamustine and rituximab (BR) followed by venetoclax for 12 months. The combination of the drugs bendamustine and rituximab is a commonly used treatment for your disease. Venetoclax is an oral drug that blocks a protein called BCL-2 which is present on CLL cells. With this combination, we hope to increase response to therapy and reduce the risk of tumor lysis syndrome. In addition, we hope to reduce the total time on therapy by limiting treatment with venetoclax to 12 months in duration. Cancers include chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).