The presence of complex karyotype (CK) does not affect survival in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) who are treated with idelalisib, according to a new analysis.

Researchers analyzed data from two clinical trials of idelalisib, given alone or in combination with rituximab, and found no significant difference in overall survival (OS) between patients with and without CK.

Karl-Anton Kreuzer, MD, of the University of Cologne (Germany), and colleagues described these findings in a letter to Leukemia.

The researchers evaluated patients with previously treated CLL who were enrolled in a phase 3 trial and received either idelalisib plus rituximab or rituximab plus placebo. Patients from either treatment arm could enroll in an extension study of idelalisib monotherapy.

There were 220 patients randomized to idelalisib plus rituximab (n = 110) or placebo plus rituximab (n = 110) in the primary study, and 161 of these patients were enrolled in the extension study.

The final analysis included 120 patients who were successfully karyotyped – 63 from the idelalisib-rituximab arm and 57 from the placebo-rituximab arm. Less than half of patients in each arm were CK-positive – 41% (26/63) of the idelalisib arm and 42% (24/57) of the placebo arm.

The researchers wrote that baseline characteristics were “mostly balanced” between the CK-positive and CK-negative groups in each treatment arm. The only significant difference was that fewer CK-positive patients in the placebo arm had a creatinine clearance of 30-59 mL/min (P = .0324).

Results

There were no significant differences in outcomes between CK-positive and CK-negative patients who received idelalisib and rituximab. The overall response rate was 81% in CK-positive patients and 89% in CK-negative patients (P = .3509). The median progression-free survival was 20.9 months and 19.4 months, respectively (P = .5848).

The median OS was 28.3 months in the CK-positive group and 49.7 months in the CK-negative group (P = .2099). The copresence of CK and del(17p), TP53 mutation, or del(11q) didn’t significantly affect OS, the researchers noted.

Among all CK-positive patients, the median OS was 28.3 months in the idelalisib-rituximab arm and 9.2 months in the placebo-rituximab arm (P = .0412).

“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.”

The researchers noted that this study has limitations, so prospective clinical trials are needed to guide treatment of patients with relapsed/refractory CLL and CK.

Both trials of idelalisib were sponsored by Gilead. The researchers reported relationships, including employment, with Gilead and other companies. They also disclosed funding from the German government and from nonprofit organizations in Germany.

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SOURCE: Kreuzer K-A et al. Leukemia. 2019 Aug 19. doi: 10.1038/s41375-019-0533-6.