Follow-up Analysis of Ixazomib, Lenalidomide and Dexamethasone Versus Lenalidomide and Dexamethasone in Routine Clinical Practice

Background: The addition of ixazomib to the doublet lenalidomide and dexamethasone (RD) in relapsed and refractory multiple myeloma (RRMM) has shown significant benefit in progression free survival (PFS) in the TOURMALINE-MM1 study. Several real-world data including our previous analysis confirmed that the combination IRD is feasible and with fair outcomes even outside the clinical trial. Here we report an updated analysis which is aimed at overall survival (OS) and the PFS2 interval which is defined as the time from the date of treatment initiation to the date of first documentation of progressive disease after initiation of further anti-myeloma treatment or death from any cause.

Methods: We analyzed a cohort of 344 patients with RRMM, 127 being treated by IRD and 217 by RD combination. The group characteristics and study design are described elsewhere. ¹ The median follow-up of the whole cohort was 28.5 months. The primary endpoint was OS, OS in patients with relapse 1-3, progression free survival (PFS), and PFS2. Secondary endpoints were response rates and toxicity profile.

For statistical analysis we used Fisher's exact test or Mann-Whitney U test. Survival measures were assessed using the Kaplan-Meier methodology, and statistical significance was assessed using the log-rank test at a significance level of α = 0.05 (all tests two-sided).

Results: The outcomes of OS in the whole cohort were already published before, with significantly longer median OS in the IRD vs RD cohort (mOS 36.6 months vs 26.0 months, p = 0.008).1 In the follow-up analysis, the medians were slightly improved, maintaining a significant difference (mOS 40.9 vs 27.1 months, p = 0.001). In patients treated within relapse 1-3, the results outcomes were even more pronounced (mOS 51.7 vs 27.8 months, p ˂ 0.001).

The median PFS was also better in the IRD cohort (mPFS 17.5 vs 12.5 months, p = 0.013) but the results did not substantially differ from our previous analysis.

The median PFS2 in the IRD vs RD cohort was significantly longer in the IRD cohort (mPFS2 29.8 vs 21.6 months, p = 0.016). The subsequent therapy included mostly pomalidomide (27.5% vs 30.8%), bortezomib (28.8% vs 28.2%) or thalidomide (10.0% vs 16.2%). Monoclonal antibodies (daratumumab, isatuximab) were more frequently used after IRD combination (21.3% vs 4.3%).

The response rates in the IRD vs RD cohort were similar as in our primary analysis: overall response rate (ORR) 73.0% vs 66.8%, with significant difference in very good partial response and better (VGPR+) 38.1% vs 26.3%. The toxicity profile did not reveal any additional safety concerns. Majority of grade 3+ toxicities included hematological toxicity (anemia, neutropenia, thrombocytopenia) and infections, with similar distribution in the cohorts.

Conclusion: The treatment of RRMM using the full oral IRD regimen in routine clinical practice is easy, safe and with significantly improved outcomes in comparison to RD doublet. Our follow-up analysis confirmed the impact on OS in patients in the whole cohort including relapse 1-3. The median PFS2 was also longer in the IRD cohort, possibly affected by more frequent use of monoclonal antibodies in the next treatment.

With support of AZV 17-29343A, NV18-03-00500, MH CZ - DRO (FNOl, 00098892), IGA-LF-2021-001.

1) Minarik J, Pika T, Radocha J. et al. Survival benefit of ixazomib, lenalidomide and dexamethasone (IRD) over lenalidomide and dexamethasone (Rd) in relapsed and refractory multiple myeloma patients in routine clinical practice. BMC Cancer 2021; 21: https://doi.org/10.1186/s12885-020-07732-1