Prolonged survival with a longer duration of maintenance lenalidomide after autologous hematopoietic stem cell transplantation for multiple myeloma

BACKGROUND: Although lenalidomide maintenance therapy has demonstrated improved outcomes after autologous hematopoietic stem cell transplantation (auto-HCT) for patients with multiple myeloma (MM), the impact of the duration of this therapy is not clearly known. METHODS: This study retrospectively analyzed all MM patients who were placed on maintenance lenalidomide after auto-HCT between January 2007 and December 2013. Progression-free survival (PFS) and overall survival (OS) were analyzed in multivariate Cox proportional hazards regression models that included the duration of maintenance as a time-dependent covariate. RESULTS: Of the 464 patients identified, 46% initiated therapy early (<4 months after auto-HCT). The median PFS and OS were 38 and 78 months, respectively. Improvements in PFS (hazard ratio [HR], 0.13; 95% confidence interval [CI], 0.04-0.38; P <.001) and OS (HR, 0.09; 95% CI, 0.03-0.26; P <.001) were seen for those on maintenance for >2 years versus those on maintenance for ≤2 years. For those on maintenance for >3 versus those on maintenance for ≤3 years, this trend continued with improvements seen in PFS (HR, 0.02; 95% CI, 0.00-0.44; P =.012) and OS (HR, 0.05; 95% CI, 0.00-0.83; P =.037). The incidence of second primary malignancies (SPMs) in the entire cohort was 3%. No differences were seen in survival between early and late initiators of maintenance lenalidomide. CONCLUSIONS: A longer duration of maintenance therapy was associated with longer survival. The incidence of SPMs was low, and they were not associated with the duration of maintenance. The timing of the initiation of maintenance had no effect on survival. Cancer 2016;122:3831–3837.