Ixazomib-based maintenance therapy after bortezomib-based induction in patients with multiple myeloma not undergoing transplantation: A real-world study

Background Maintenance therapy with proteasome inhibitors (PIs) can improve outcomes of multiple myeloma (MM) patients, however, the neurotoxicity and parenteral route of bortezomib limit its long-term use. An efficacious, tolerable, and convenient PI option is needed. Methods In this single-center, real-world study, we retrospectively analyzed the outcome and safety profile of ixazomib-based maintenance therapy in patients who plateaued with the responses of steady disease or better after bortezomib-based induction therapy in MM patients not undergoing transplantation. Results Of all the 71 patients, 37 cases (52.1%) were newly diagnosed MM (NDMM) and 34 cases (47.9%) were relapsed and/or refractory MM (RRMM). The overall response rate (ORR) was 81.7%, including 34 patients (47.9%) with a very good response rate or better (>= VGPR) after a median of nine cycles (6-14) of bortezomib-based induction therapy. Then the ORR was transformed to 74.6% including 39 patients of >= VGPR (54.9%) after a median of six courses (2-25) of ixazomib-based maintenance therapy. Of these, 18 patients (25.4%) exhibited responses deepened. With 26.5 months median follow-up, median progression-free survival (PFS) was 28.4 and 16.5 months from the start of bortezomib and 16.2 and 10.0 months from the initiation of ixazomib in NDMM and RRMM group, respectively. Moreover, responses deepened during the maintenance phase (hazard ratio: 0.270, p = 0.007), and responses of >= VGPR during the induction phase (hazard ratio: 0.218, p < 0.001) were confirmed to independently predict longer PFS after multivariate analyses. Severe adverse events (grade 3/4) were relatively rare. Bortezomib-emergent peripheral neuritis (PN) was significantly relived after the transition to ixazomib (p < 0.001). Conclusion This real-world analysis has demonstrated oral ixazomib is a favorable option of long-term administration for maintenance with efficacy and feasibility and confirmed the association between deepening responses with ixazomib and prolonged PFS.