Abstract CT158: Unmutated IGHV is not an adverse predictor of outcome to therapy with ibrutinib in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL)

Abstract

Abstract Background: Patients (pts) with CLL/SLL who use unmutated IGHV (u-CLL) have a less favorable outcome with standard chemotherapy than pts who use mutated IGHV (m-CLL). Ibrutinib (ibr) inhibits B-cell receptor signaling through Bruton’s tyrosine kinase and has robust clinical activity against CLL. This integrated analysis of 3 phase 3 studies examined the impact of IGHV status on ibr- and comparator (comp)-treated pts. Methods: Pooled data from 3 studies of ibr (420 mg/d) in CLL/SLL pts (RESONATE: relapsed/refractory [R/R] pts, ibr vs ≤ 24 weeks ofatumumab; RESONATE-2: treatment-naïve [TN] pts ≥ 65 yrs of age [no del17p], ibr vs ≤ 12 cycles chlorambucil; HELIOS: R/R pts [no del17p], ≤ 6 cycles bendamustine-rituximab with ibr vs placebo) were analyzed by IGHV status. Analyses included Kaplan-Meier method (overall survival [OS]; progression-free survival [PFS]); log-rank test (group comparisons); and Cox multivariate analysis (prognostic factors; Table). Results: For 491 ibr- (366 u-CLL, 125 m-CLL) and 494 comp-treated (351 u-CLL, 143 m-CLL) pts with IGHV data, baseline characteristics were similar for u-CLL vs m-CLL, except for the proportions of pts who were TN (17 vs 31%), had bulky disease (60 vs 37%), or had CLL cells with del11q (32 vs 16%). Median follow up was 21.4 mos for ibr and 20.6 mos for comp. PFS and OS were similar for u-CLL and m-CLL ibr-treated pts; u-CLL had poorer outcomes than m-CLL in comp-treated pts, which remained after adjustment for prognostic factors (Table). Ibr treatment was more effective than comp regardless of IGHV status. Incidence of adverse events (AEs) was similar between groups. For ibr vs comp pts (u-CLL/m-CLL): serious AEs: 49% (50%/47%) vs 36.5% (37%/35%); AEs that led to discontinuation: 12% (11%/15%) vs 13% (13%/14%); death within 30 days of last dose: 5% (6%/3%) vs 5% (6%/2%). Conclusions: U-CLL was an adverse predictor of outcome for comp-treated, but not for ibr-treated pts. Table.Efficacy Outcomes in Ibr- and Comparator-Treated Patients by IGHV Mutation StatusIbrutinib (N=491)Comparator (N =494)u-CLL (n=717)m-CLL (n=268)u-CLL(n=366): m-CLL(n=125)u-CLL(n=351): m-CLL(n=143)Ibr(n=366): Comp(n=351)Ibr (n=125): Comp (n=143)PFS24-month rate HR78%:81%10%:32%78%:10%81%:32%0.93a1.99a0.12b0.21bp = 0.78p < 0.0001p < 0.0001p <0.0001Adjusted HRc1.02a1.94a0.11b0.17bp = 0.93p < 0.0001p < 0.0001p < 0.0001OS24-month rate HR88%:89%78%:87%88%:78%89%:87%0.95a1.96a0.49b0.85b,ep = 0.86p = 0.02p < 0.01p = 0.66Adjusted HRc1.21a2.10a0.49bNAp =0.57p = 0.01p < 0.001Response ratesu-CLLm-CLLu-CLLm-CLLIbrCompIbrCompORR, %d8990475189479051p = 0.96p = 0.36p < 0.0001p < 0.0001CR, %d221546224156p = 0.10p = 0.44p < 0.0001p = 0.01CI, confidence interval; CR, complete response; HR, hazard ratio; ORR, overall response rate; NA, not applicable. aHR < 1 favors unmutated. bHR < 1 favors ibrutinib. cMultivariate Cox model adjusted for age, sex, current Rai stage, baseline ECOG performance status score, del11q, del17p, number of prior therapies, and cytopenias. dp value is from a Cochran-Mantel-Haenszel chi-square test. eInsufficient number of events prevents meaningful analysis, only 13 and 16 events observed in ibr and comp groups, respectively, and 46 (32%) pts in comp arm crossed over to ibr arm; interpret results with caution. Citation Format: Thomas J. Kipps, Graeme Fraser, Steven Coutre, Jennifer R. Brown, Jacqueline C. Barrientos, Paul M. Barr, John C. Byrd, Susan M. O'Brien, Marie-Sarah Dilhuydy, Stephen Devereux, Ulrich Jaeger, Carol Moreno, Paula Cramer, Stephan Stilgenbauer, Asher A. Chanan-Khan, Michelle Mahler, Mariya Salman, Mei Cheng, Anil Londhe, Joi Ninomoto, Angela Howes, Danelle James, Michael Hallek. Unmutated IGHV is not an adverse predictor of outcome to therapy with ibrutinib in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT158. doi:10.1158/1538-7445.AM2017-CT158