Background: In two randomized phase III trials (MM-009 and MM-010), lenalidomide plus dexamethasone significantly prolonged time to progression and overall survival (OS) in patients with relapsed/refractory multiple myeloma compared with dexamethasone alone. In both trials the treatment was continued until disease progression or unacceptable toxicity. We conducted a subanalysis to determine if continuing therapy after achieving≥partial response (PR) improved survival.
Patients and methods: Data were collected on 212 patients who were treated with lenalidomide plus dexamethasone and achieved≥PR. Kaplan-Meier survival estimates were compared between patients on continued treatment versus patients discontinuing therapy because of adverse events, withdrawal of consent, or other reasons. Time-dependent multivariate regression analyses were used to determine the benefit of continuing treatment with lenalidomide.
Results: A total of 174 patients received continued treatment until disease progression or death, and 38 patients discontinued therapy without progression. There was a trend toward longer median OS in patients who continued therapy (50.9 months vs. 35.0 months; P=.0594). When controlling for the number of previous antimyeloma therapies, β2-microglobulin levels, and Durie-Salmon stage (which adversely affected survival in these patients), continued lenalidomide treatment (HR, 0.137; 95% CI, 0.045-0.417; P=.0005) or each additional cycle of lenalidomide (HR, 0.921; 95% CI, 0.886-0.957; P<.0001) were both associated with longer survival.
Conclusion: Continued lenalidomide treatment until disease progression after achievement of ≥PR is associated with a significant survival advantage when controlling for patient characteristics. These findings should be confirmed in a prospectively designed trial.
Trial registration: ClinicalTrials.gov NCT00056160 NCT00424047.