Comparison of lenalidomide in combination with dexamethasone to dexamethasone alone in patients who have received prior thalidomide in relapsed or refractory multiple myeloma

7522 Background: Lenalidomide (len), an analog of thalidomide (thal) is a novel, oral immunomodulatory agent that is effective against multiple myeloma (MM). Two randomized, Phase III trials (MM009 and MM010) have recently demonstrated superior responses and overall survival (OS) for patients (pts) treated with len and dexamethasone (dex) in comparison with dex-placebo. This is a prospective subgroup analysis to assess the impact of prior therapy with thal on the sensitivity of MM to subsequent lenalidomide. Methods: We evaluated 692 pts from both trials (MM009 and MM010). The pts had relapsed/refractory MM, were not refractory to dex and were randomized to receive either len (25 mg daily for 3 weeks (wks) every 4 wks) plus dex (40 mg on days 1–4, 9–12, 17–20 every 4 wks for 4 cycles, then 40 mg on days 1–4 every subsequent cycle) or placebo plus dex. Standard criteria were used to evaluate response and TTP. Results: Pooled data from 692 pts showed superior median TTP (48.1 vs 20.1 wks) and OR (59.2% vs 22.5%) in pts treated with len/dex compared to dex-placebo (p <0.001). Although subgroup analysis of pts with prior thal therapy revealed that pts who received len/dex had significantly improved OR, PR CR and median TTP than pts who received dex-placebo, OR, CR and TTP were highest in len/dex pts not previously treated with thal. Multivariate analysis indicates that after controlling for the treatment factor and baseline disease characteristics, whether or not pt had prior exposure to thal is a marginally significant variable to predict TTP. The risk of deep venous thrombosis and pulmonary embolism in these subgroups will be updated on further analysis. Conclusions: Lenalidomide in combination with dexamethasone is more effective than dexamethasone-placebo regardless of prior thalidomide in relapsed/refractory multiple myeloma. [Table: see text] [Table: see text]