Single-agent ibrutinib in treatment-naïve and relapsed/refractory chronic lymphocytic leukemia: a 5-year experience

We previously reported durable responses and manageable safety of ibrutinib from a 3-year follow-up of treatment-naïve (TN) older patients (≥65 years of age) and relapsed/refractory (R/R) patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). We now report on long-term efficacy and safety with median follow-up of 5 years in this patient population with TN (N = 31) and R/R (N = 101) CLL/SLL. With the current 5-year follow-up, ibrutinib continues to yield a high overall response rate of 89%, with complete response rates increasing over time to 29% in TN patients and 10% in R/R patients. The median progression-free survival (PFS) was not reached in TN patients. The 5-year PFS rate was 92% in TN patients and 44% in R/R patients. Median PFS in R/R patients was 51 months; in those with del(11q), del(17p), and unmutated IGHV, it was 51, 26, and 43 months, respectively, demonstrating long-term efficacy of ibrutinib in some high-risk subgroups. Survival outcomes were less robust for R/R patients with del(17p) and those who received more prior therapies. The onset of grade ≥3 cytopenias, such as neutropenia and thrombocytopenia, decreased over time. Treatment--limiting adverse events were more frequent during the first year compared with subsequent periods. These results demonstrate sustained efficacy and acceptable tolerability of ibrutinib over an extended time, providing the longest experience for Bruton tyrosine kinase inhibitor treatment in patients with CLL/SLL. These trials were registered at www.clinicaltrials.gov as #NCT01105247 and #NCT01109069.