Measurable Residual Disease–Guided Therapy for Chronic Lymphocytic Leukemia

BACKGROUND: An interim analysis of progression-free survival in this trial showed that ibrutinib-venetoclax was superior to fludarabine-cyclophosphamide-rituximab (FCR) among patients with chronic lymphocytic leukemia (CLL). Whether ibrutinib-venetoclax is more effective than ibrutinib alone is unclear. METHODS: In this phase 3, multicenter, open-label trial, we randomly assigned patients with CLL to receive ibrutinib-venetoclax, ibrutinib alone, or FCR. The primary end points were undetectable measurable residual disease (MRD) in bone marrow within 2 years in the ibrutinib-venetoclax group as compared with the ibrutinib-alone group and progression-free survival in the ibrutinib-venetoclax group as compared with the FCR group. A powered secondary end point was progression-free survival in the ibrutinib-venetoclax group as compared with the ibrutinib-alone group. Other secondary end points included overall survival. RESULTS: A total of 172 of the 260 participants (66.2%) in the ibrutinib-venetoclax group had undetectable MRD in bone marrow within 2 years, as compared with none of the 263 participants in the ibrutinib-alone group (P<0.001) and 127 of the 263 participants (48.3%) in the FCR group. With a median follow-up of 62.2 months, disease progression or death occurred in 18 participants (6.9%) in the ibrutinib-venetoclax group, as compared with 59 (22.4%) in the ibrutinib-alone group (hazard ratio, 0.29; 95% confidence interval [CI], 0.17 to 0.49; P<0.001) and 112 (42.6%) in the FCR group (hazard ratio, 0.13; 95% CI, 0.08 to 0.21; P<0.001). Progression-free survival at 5 years was 93.9% with ibrutinib-venetoclax, 79.0% with ibrutinib alone, and 58.1% with FCR. Death occurred in 11 participants (4.2%) in the ibrutinib-venetoclax group, as compared with 26 (9.9%) in the ibrutinib-alone group (hazard ratio, 0.41; 95% CI, 0.20 to 0.83) and 39 (14.8%) in the FCR group (hazard ratio, 0.26; 95% CI, 0.13 to 0.50). Sudden death occurred in 3, 8, and 4 participants in the ibrutinib-venetoclax, ibrutinib-alone, and FCR groups, respectively. CONCLUSIONS: With extended follow-up and increased enrollment, our trial showed that undetectable MRD and extended progression-free survival were more common with ibrutinib-venetoclax than with ibrutinib alone or FCR. The results for overall survival were also consistent with a benefit of ibrutinib-venetoclax. (Funded by Cancer Research UK and others; FLAIR ISRCTN Registry number, ISRCTN01844152; EudraCT number, 2013-001944-76.).