Why This Study Matters
High-risk multiple myeloma — defined by two or more high-risk cytogenetic abnormalities, high-risk gene expression profiling, or plasma cell leukaemia — has long carried a substantially worse prognosis than standard-risk disease, even with modern quadruplet induction regimens. Roughly 20–25% of newly diagnosed myeloma falls into this high-risk category. The phase 2 OPTIMUM/MUKnine trial tested whether front-loading intensified, extended treatment, guided by molecular risk stratification at diagnosis, could narrow that gap.
This report is the 5-year follow-up of the trial, extending an earlier interim analysis that established the regimen's 18-month progression-free survival as its original primary endpoint.
Study Design
OPTIMUM/MUKnine is a multicentre, externally controlled, Bayesian-design phase 2 trial conducted at 22 centres across the UK. Rather than randomizing patients against a concurrent control arm, the trial compared outcomes on the intensified OPTIMUM regimen against a molecularly matched external control cohort drawn from the earlier Myeloma XI trial. Patients on the OPTIMUM regimen received induction with daratumumab, cyclophosphamide, bortezomib, lenalidomide, and dexamethasone; autologous stem-cell transplantation with melphalan-bortezomib conditioning; two-part extended consolidation; and maintenance with lenalidomide plus daratumumab continued until disease progression, unacceptable toxicity, or withdrawal.
Patient Population
Eligible patients were adults aged 18 or older with newly diagnosed high-risk multiple myeloma or plasma cell leukaemia, measurable disease per International Myeloma Working Group criteria, up to two prior induction cycles, and an ECOG Performance Status of 2 or less. Between September 29, 2017, and September 24, 2019, 108 participants were recruited and 107 were included in the analysis. The external control comprised 120 genetically matched patients from the Myeloma XI trial, followed for a median of 117.8 months — far longer than OPTIMUM's median follow-up of 71.1 months, reflecting the two trials' different enrollment eras.
Survival Results
This analysis reports progression-free survival (PFS), a second progression-free survival measure (PFS2 — time to second disease progression or death), and overall survival (OS) at 5 years of follow-up.
| Endpoint | OPTIMUM (median) | Myeloma XI external control (median) | Hazard ratio (95% CI) |
|---|---|---|---|
| Progression-free survival | Not reached | 24.4 months | 0.32 (0.22–0.45) |
| Overall survival | Not reached | 57.4 months | 0.43 (0.28–0.65) |
| PFS2 | Not reached | 43.9 months | 0.26 (0.17–0.41) |
Subgroup Analyses
The trial examined outcomes by high-risk feature at entry — two or more high-risk cytogenetic abnormalities, high-risk gene expression profiling, both together, and plasma cell leukaemia — with these subgroups selected post hoc rather than prespecified. The published abstract reports only a qualitative summary: the survival benefit was consistent across high-risk multiple myeloma subgroups, except for patients with three or more high-risk cytogenetic abnormalities, where the benefit was not consistent with the overall result. No subgroup-specific hazard ratios, confidence intervals, or P values are reported for any individual subgroup.
Safety Profile
This 5-year follow-up report does not include adverse-event rates or a safety summary; it focuses on survival outcomes across molecular subgroups. Safety data for the OPTIMUM regimen were reported separately in the trial's earlier primary-endpoint publication.
Interpretation and Broader Context
Taken together, these 5-year results suggest that upfront molecular risk-stratification, paired with intensified induction, extended consolidation, and continued maintenance, can shift a historically poor prognosis for high-risk multiple myeloma toward outcomes that begin to approach those typically seen in standard-risk disease. The authors frame the findings as supporting broader implementation of molecular diagnostics — cytogenetics and gene-expression profiling — at diagnosis, so that treatment intensity can be tailored to a patient's molecular risk. The exception, patients with three or more high-risk cytogenetic abnormalities, is flagged as an area needing further study, suggesting this subset may need a different or more intensive approach.
Limitations
OPTIMUM/MUKnine is a single-arm trial without a concurrent randomized control; its comparator is an externally controlled cohort from a separate trial (Myeloma XI), matched on molecular features but not randomized against the OPTIMUM regimen, which limits how directly the survival differences can be attributed to treatment rather than to other differences between the two trial populations and eras. The two cohorts were followed for very different lengths of time (a median of 71.1 months for OPTIMUM versus 117.8 months for Myeloma XI), and the high-risk subgroup analyses were selected post hoc rather than prespecified and powered, so the finding that patients with three or more high-risk cytogenetic abnormalities did not show the same consistent benefit should be read as hypothesis-generating rather than definitive. This report is an ahead-of-print publication and does not include adverse-event data from the 5-year follow-up.
At 5 years of follow-up, intensified, risk-stratified therapy in OPTIMUM/MUKnine was associated with markedly longer progression-free and overall survival than a molecularly matched external control cohort, with median survival not yet reached in the treated group. Because the trial used an externally controlled rather than randomized design, and because the two cohorts differed in follow-up duration and enrollment era, these results support further study of risk-stratified intensive therapy rather than establishing a confirmed, randomized survival benefit.