Background
Smoldering multiple myeloma (SMM) carries variable progression risk to symptomatic disease, and the standard had been observation. Phase III ECOG-ACRIN E3A06 tested whether early single-agent lenalidomide delays progression in intermediate/high-risk SMM.
Interventions and follow up
Arm A: Lenalidomide 25 mg orally days 1-21 of a 28-day cycle (n=92).
Arm B: Observation (n=90).
Primary endpoint: PFS, defined as progression to symptomatic myeloma (end-organ damage) or biochemical progression.
mFollow up: Median 35 months.
Arm B: Observation (n=90).
Primary endpoint: PFS, defined as progression to symptomatic myeloma (end-organ damage) or biochemical progression.
mFollow up: Median 35 months.
Results
PFS: favored lenalidomide — HR 0.28; 95% CI 0.12 to 0.62; P=.002.
1-, 2-, 3-yr PFS: 98%, 93%, 91% (lenalidomide) vs 89%, 76%, 66% (observation).
Response rate: 50% (95% CI 39% to 61%) with lenalidomide vs no responses with observation.
OS: no significant difference between arms.
1-, 2-, 3-yr PFS: 98%, 93%, 91% (lenalidomide) vs 89%, 76%, 66% (observation).
Response rate: 50% (95% CI 39% to 61%) with lenalidomide vs no responses with observation.
OS: no significant difference between arms.
Adverse events
Overall: Grade 3-4 nonhematologic adverse events occurred in 28% of the lenalidomide arm.
Common nonhematologic: fatigue, rash, and infections were the most frequent toxicities.
Hematologic: grade 3+ neutropenia was infrequent.
Discontinuation: 51% of lenalidomide-treated patients discontinued, largely for toxicity.
Common nonhematologic: fatigue, rash, and infections were the most frequent toxicities.
Hematologic: grade 3+ neutropenia was infrequent.
Discontinuation: 51% of lenalidomide-treated patients discontinued, largely for toxicity.
Conclusions
Early single-agent lenalidomide significantly delays progression to symptomatic myeloma in intermediate/high-risk SMM, with the greatest benefit in high-risk patients, at the cost of substantial toxicity-driven discontinuation.
Key Limitations
No OS benefit demonstrated and follow-up was relatively short; the high discontinuation rate (51%) limits real-world durability. Whether delaying progression translates to long-term survival or simply earlier treatment of a chronic condition remains debated.
Clinical Context
E3A06 is the largest randomized SMM trial and supports considering lenalidomide for high-risk SMM, though observation remains standard for most patients per IMWG and ASCO/ESMO guidance. It complements the QuiRedex (Rd) data and informs ongoing debate over early intervention versus active monitoring.
References