CLL breakthrough: stopping treatment may be possible for some patients

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Screening Phase Inclusion Criteria: * ≥ 18-years-old * Diagnosis of chronic lymphocytic leukemia or small lymphocytic lymphoma confirmed by the enrolling institution * Receiving treatment or planning to receive treatment within 30 days with a venetoclax-based regimen as defined below: * Venetoclax monotherapy * Venetoclax in combination with anti CD20 monoclonal antibody (Patients must have completed the anti CD20 monoclonal antibody portion of the regimen prior to discontinuing therapy) * Patient has or will have specimen to identify the CLL or SLL clone(s) for future MRD assessments by clonoSEQ® defined as any of the following: * 3-5 bone marrow aspirate slides (banked), 3-5 FFPE slides (banked), banked tumor cells or banked DNA collected from the patient at any time from original diagnosis of CLL or SLL to present * Peripheral blood, marrow, or lymph node involvement for fresh sample collection * The screening ID sample (high disease burden sample) can be sent prior to start of venetoclax-based therapy to identify the clone for tracking. Study Intervention Phase Inclusion Criteria: * Patients must have received venetoclax-based therapy for at least 6 months (including dose interruptions) * If receiving venetoclax in combination with anti-CD20 monoclonal antibody, patients must have completed or discontinued the anti CD20 monoclonal antibody portion of the regimen prior to discontinuing therapy * Patients must have two MRD-negative assessments (defined by ≥ 10\^-5 sensitivity) on the peripheral blood by the clonoSEQ® assay at least 28 days apart. Given that MRD status is a dynamic endpoint which may improve with time, if a patient is screen failure based on MRD status (i.e. MRD positive at the 10-5 sensitivity), they may be rescreened to assess for study eligibility. * Patients must have achieved a complete or partial remission with the venetoclax-based regimen. Criteria for remission are per iwCLL 2018 guidelines. For this protocol, bone marrow biopsy/aspirate evaluation is not necessary to determine remission status. Exclusion Criteria (both study phases): * Ongoing participation in a clinical trial that supplies venetoclax and/or anti CD20 monoclonal antibody * Unwilling or unable to participate in all required study evaluations and procedures. * Unable to understand the purpose and risks of the study and to provide a signed and dated informed consent form (ICF) and authorization to use protected health information (in accordance with national and local patient privacy regulations).