Outcomes of Patients With Chronic Lymphocytic Leukemia Treated With First-Line Idelalisib Plus Rituximab After Cessation of Treatment for Toxicity

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Abstract

BACKGROUND:

More active therapies are needed for older and unfit patients with chronic lymphocytic leukemia (CLL) who are not eligible for chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab. The phosphyotidylinositol-3-kinase δ inhibitor idelalisib is effective in patients with treatment-naive and relapsed/refractory CLL as monotherapy and in combination with rituximab, but it can be associated with treatment-limiting adverse events, particularly diarrhea/colitis. The outcomes for patients who cease treatment for adverse events have not been previously described.

METHODS:

The authors analyzed long-term follow-up data from 40 treatment-naïve patients aged ≥65 years who received treatment at The University of Texas MD Anderson Cancer Center on a phase 2 study of idelalisib plus rituximab for CLL.

RESULTS:

In patients who permanently ceased treatment because of toxicity, the time to subsequent disease progression was analyzed according to baseline characteristics. Fifteen patients permanently ceased therapy (PCT) because of toxicity (PCTTOX), most commonly diarrhea/colitis (n = 7), at a median of 11 months after commencing treatment. PCTTOX was associated with a higher risk of subsequent disease progression (hazard ratio, 6.61; 95% confidence interval, 1.77-16.15) relative to that observed in patients who remained on therapy. Ten patients subsequently progressed, and 7 required salvage therapy; 5 patients remained progression-free at a median of 23.3 months (range, 8.5-28.6 months). Patients who were positive for ζ-associated protein-70 had more rapid disease progression after treatment cessation (P = .048). There were no CLL-related deaths.

CONCLUSIONS:

PCTTOX is the major determinant of PFS in patients who receive first-line idelalisib-based treatment. However, a subgroup of patients with favorable biologic characteristics has prolonged PFS, even after PCTTOX. The absence of CLL-related deaths indicates that salvage treatment is generally successful after PCTTOX.

Toxicity, likely immunologically mediated, is the major limitation to achieving long-term remission during first-line treatment with idelalisib plus rituximab for patients with chronic lymphocytic leukemia. Overall survival is favorable despite the high rate of treatment cessation caused by toxicity.

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