Testing the Addition of a New Anti-cancer Drug, Venetoclax, to the Usual Treatment (Ibrutinib and Obinutuzumab) in Untreated, Older Patients With Chronic Lymphocytic Leukemia

PRIMARY OBJECTIVE: I. To compare the progression-free survival (PFS) between control treatment and experimental treatment strategies: ibrutinib/obinutuzumab (IO) with ibrutinib maintenance (IM) versus ibrutinib/venetoclax/obinutuzumab (IVO) regardless of IM or observation. SECONDARY OBJECTIVES: I. To compare bone marrow (BM) minimal residual disease (MRD)- complete response (CR) rates, MRD- rates, and depth of response at cycle 15 day 1 between patients treated with IO versus IVO. II. To compare overall survival (OS) between the control and experimental treatment strategies: IO with IM versus IVO regardless of IM or observation. III. To compare the 5-year PFS and overall survival (OS) for the control and experimental treatment strategies: IO with IM versus IVO regardless of IM or observation. IV. To describe the toxicity profile for each of the treatment strategies and by each treatment course. CORRELATIVES SCIENCE OBJECTIVES: I. To compare MRD status between blood and bone marrow at the end of induction treatment/cycle 15 day 1 to determine whether blood MRD can be used as a surrogate to bone marrow MRD with these treatment regimens. II. To compare peripheral blood MRD status by standard central flow cytometry to next generation sequencing (NGS) using ClonoSeq technique to determine the agreement in MRD negativity of the two techniques. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive ibrutinib orally (PO) once daily (QD) on days 1-28. Patients also receive obinutuzumab intravenously (IV) on days 1, 2, 8, and 15 of cycle 1, and on day 1 of cycles 2-6. Treatment repeats every 28 days for up to 14 cycles in the absence of disease progression or unacceptable toxicity. Beginning cycle 15, patients receive ibrutinib PO QD every 28 days in the absence of disease progression or unacceptable toxicity. ARM II: Patients receive ibrutinib PO QD on days 1-28. Patients also receive obinutuzumab IV on days 1, 2, 8, and 15 of cycle 1, and on day 1 of cycles 2-6. Beginning cycle 3, patients also receive venetoclax PO QD on days 1-28. Treatment repeats every 28 days for 14 cycles in the absence of disease progression or unacceptable toxicity. All patients will then receive a 15th cycle of ibrutinib. Beginning cycle 16, patients who do not achieve a BM MRD negative CR, receive ibrutinib PO QD every 28 days in the absence of disease progression or unacceptable toxicity. Patients who achieve a BM MRD negative CR undergo observation every 3 cycles for 6 years, then every 6 cycles thereafter. After completion of study treatment, patients are followed every 6 months until 10 years from registration.