Permanently ceased therapy of idelalisib plus rituximab due to toxicity was associated with an increased risk of subsequent disease progression in patients with chronic lymphocytic leukemia (CLL) as compared with those who remained on therapy, a study published in the journal Cancer has shown.1

Although fludarabine, cyclophosphamide, and rituximab is an effective regimen for CLL, older and unfit patients are often not eligible to receive this chemoimmunotherapy modality.

The phosphyotidylinositol-3-kinase δ inhibitor idelalisib is effective in patients with treatment-naïve and relapsed/refractory disease as a single-agent or in combination with rituximab; however, it can be associated with treatment-limiting toxicities, particularly diarrhea/colitis. Therefore, researchers sought to investigate the clinical outcomes of patients who discontinue idelalisib plus rituximab due to adverse events.

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For the study, researchers analyzed long-term follow-up data from 40 treatment-naïve patients aged 65 years or older who received treatment at The University of Texas MD Anderson Cancer Center in Houston, TX, as part of a phase 2 trial. All patients received idelalisib plus rituximab.

Results showed that at a median of 11 months after initiating therapy, 15 patients permanently discontinued therapy because of toxicity, of which 7 ceased treatment due to diarrhea/colitis.

Researchers found that patients who permanently ceased therapy due to adverse events were more likely to experience subsequent disease progression compared with those who continued treatment (HR, 6.61; 95% CI, 1.77-16.15). Of those 15 patients, 10 subsequently progressed, and 7 required salvage therapy. The other 5 patients remained progression-free at a median of 23.3 months.

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Further, there were no CLL-related deaths, suggesting that salvage therapy is generally successful after cessation of idelalisib plus rituximab due to toxicity.

The study also demonstrated that patients who tested positive for ζ-associated protein-70 had more rapid disease progression following treatment discontinuation (P = .048).               


  1. Thompson PA, Stingo F, Keating MJ, et al. Outcomes of patients with chronic lymphocytic leukemia treated with first-line idelalisib plus rituximab after cessation of treatment for toxicity [published online ahead of print May 16, 2016]. Cancer. doi: 10.1002/cncr.30069.