Combination treatment with idelalisib plus rituximab may have a beneficial effect compared with rituximab alone in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) regardless of the presence of a complex karyotype (CK), according to the results of a recent post-hoc analysis.

The study was really an exploratory analysis of 2 studies: a primary study comparing rituximab with or without idelalisib and an extension study of idelalisib monotherapy.

The original study randomly assigned 220 patients to idelalisib-rituximab or placebo-rituximab. This study was closed early because of the superior efficacy of the idelalisib-rituximab regimen, according to researchers. The extension study included 161 patients from the primary study.

Researchers looked at clinical outcomes of patients treated with idelalisib from both studies with or without CKs. Successful karyotypes were obtained in 127 patients of the original 220 patients: 57% in the idelalisib arm and 52% in the placebo arm.

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About 40% of patients in both arms were CK-positive. A higher percentage of patients with CK also had del17p and/or TP53 mutation compared with patients who were CK-negative.

With a median follow-up of 29.2 months, 81% of CK-positive patients and 89% of CK-negative patients responded to idelalisib/rituximab. Additionally, progression-free survival was also similar between CK-positive and CK-negative patients, with a median of about 20 months.

Death occurred in half of CK-positive patients who were assigned to receive idelalisib-rituximab compared with 66.7% of patients treated with placebo-rituximab. Median overall survival was 28.3 months in the CK-positive group treated with idelalisib-rituximab compared with 9.2 months in CK-positive patients treated with placebo-rituximab.

No difference in overall survival was noted between CK-positive and CK-negative patients treated with idelalisib-rituximab.

“Our analysis suggests that CK-positive patients treated with idelalisib/rituximab did not exhibit a significantly shortened survival compared with those who were CK-negative,” the researchers wrote. “In addition, the primary beneficial effect of adding idelalisib to rituximab treatment in relapsed/refractory CLL patients with CK was reflected in OS prolongation compared to those who received only rituximab.”

Disclosure: Some of the authors reported financial ties to pharmaceutical companies. For a full list of disclosures, please refer to the primary study.

Reference

Kreuzer K-A, Furman RR, Stilgenbauer S, et al. The impact of complex karyotype of the overall survival of patients with relapsed chronic lymphocytic leukemia treated with idelalisib plus rituximab [published online August 19, 2019]. Leukemia. doi: 10.1038/s41375-019-0533-6