THURSDAY, Aug. 1, 2019 (HealthDay News) — For patients with previously untreated chronic lymphocytic leukemia (CLL), ibrutinib-rituximab is more efficacious than chemoimmunotherapy, according to a study published in the Aug. 1 issue of the New England Journal of Medicine.

Tait D. Shanafelt, M.D., from Stanford University in California, and colleagues randomly assigned 529 patients (aged ≤70 years) with previously untreated CLL in a 2:1 ratio to receive either ibrutinib and rituximab for six cycles (after a single cycle of ibrutinib alone) followed by ibrutinib until disease progression (354 patients) or chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab for six cycles (175 patients).

The researchers found that progression-free survival was superior in the ibrutinib-rituximab versus chemoimmunotherapy group (89.4 versus 72.9 percent at three years; hazard ratio for progression or death, 0.35; 95 percent confidence interval [CI], 0.22 to 0.56); the results met the protocol-defined efficacy threshold for the interim analysis. Overall survival also favored ibrutinib-rituximab versus chemoimmunotherapy (98.8 versus 91.5 percent at three years; hazard ratio for death, 0.17; 95 percent CI, 0.05 to 0.54). Ibrutinib-rituximab resulted in better progression-free survival than chemoimmunotherapy in patients without immunoglobulin heavy-chain variable region (IGHV) mutation (90.7 versus 62.5 percent at three years; hazard ratio for progression or death, 0.26; 95 percent CI, 0.14 to 0.50). For patients with IGHV mutation, three-year progression-free survival was 87.7 and 88.0 percent, respectively (hazard ratio for progression or death, 0.44; 95 percent CI, 0.14 to 1.36). The two groups had a similar incidence of adverse events of grade 3 or higher (80.1 versus 79.7 percent).

“Indefinite use of ibrutinib therapy has been associated with substantial expense and the potential for long-term toxic effects and may increase the risk of clonal selection leading to drug resistance,” the authors write.

Several authors disclosed financial ties to pharmaceutical companies, including Pharmacyclics, which manufactures ibrutinib and partially funded the study.

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