Comparative efficacy of zanubrutinib plus obinutuzumab versus last prior treatment in relapsed/refractory follicular lymphoma: growth modulation index analysis from the ROSEWOOD study

Background:The phase II ROSEWOOD study (NCT03332017) compared zanubrutinib plus obinutuzumab (ZO) with obinutuzumab monotherapy (O) in patients with relapsed/refractory (R/R) follicular lymphoma (FL) who had received two or more prior lines of systemic therapy.Median progression-free survival (PFS) was longer with ZO versus O 28.0 versus 10.4 months; hazard ratio 0.50, 95% confidence interval (CI) 0.33-0.75. Materials and methods:In this post hoc analysis, an intra-patient comparative analysis was carried out using the growth modulation index (GMI) to analyze the efficacy of ZO versus the last prior treatment received by patients in the ROSEWOOD study.A GMI of 1.33 was used as a threshold for significant clinical activity.Results: In the overall population, median GMI was 2.7 (95% CI 1.6-4.9) in the ZO arm and 0.9 (95% CI 0.5-1.7) in the O arm.Analysis in subgroups of clinical interest in the ZO arm showed that PFS was longer with ZO than with the last prior treatment, and median GMI was 1.33 in all subgroups tested.Overall, PFS had improved (GMI 1.33) in >60% of patients with R/R FL who received ZO versus their last prior treatment.Conclusions: This GMI analysis further supports the benefit of ZO as a novel therapeutic option for patients with R/R FL.