2. Patients must have received at least 12 months of ibrutinib therapy and have measurable CLL by at least one of the following: Absolute monoclonal lymphocyte count > 4000/microL; OR - Measurable lymph nodes with at least one node >1.5 cm in diameter on CT; OR - Bone marrow with >/= 30% lymphocytes on aspirate differential; OR - Detectable CLL cells using a standardized flow cytometry assay for minimal residual disease