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Primary results from the phase 3 RESONATE-2 study demonstrated superior efficacy and tolerability with ibrutinib versus chlorambucil in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Here, we describe characteristics and outcomes of patients who received ibrutinib treatment for ≥5 years in RESONATE-2. Patients aged ≥65 years with previously untreated CLL/SLL, without del(17p), were randomly assigned 1:1 to once-daily ibrutinib 420 mg until disease progression/unacceptable toxicity (n = 136) or chlorambucil 0.5–0.8 mg/kg for ≤12 cycles (n = 133). Baseline characteristics in ibrutinib-randomized patients (n = 136) were generally similar between patients on ibrutinib treatment for ≥5 years (n = 79) versus those on treatment for n = 57). In patients on ibrutinib treatment for ≥5 years, complete response rates improved over time, reaching 42% by 5 years. Estimated 7-year progression-free survival and overall survival rates were 82% and 94%, respectively. Adverse events (AEs) led to dose reductions in 16/79 patients (20%); these AEs were resolved for 13/16 patients (81%). AEs led to dose holds (≥7 days) in 45/79 patients (57%); these AEs were resolved for 43/45 patients (96%). More than half (58%) of ibrutinib-randomized patients benefitted from ibrutinib treatment for ≥5 years regardless of baseline characteristics. Dose modification resolved AEs for most patients, thereby facilitating continued treatment.