Analysis of the Efficacy of Thalidomide Plus Dexamethasone-Based Regimens in Patients With Relapsed/Refractory Multiple Myeloma Who Received Prior Chemotherapy, Including Bortezomib and Lenalidomide: KMM-166 Study

Background: For patients with multiple myeloma (MM) that relapsed after treatment with bortezomib- and lenalidomide-based regimens, there were no other treatment options in Korea until 2016. We aimed to determine the efficacy of thalidomide plus dexamethasone-based regimens in patients with relapsed/refractory MM (RRMM). Patients and Methods: We conducted a multicenter retrospective analysis in Korea for patients with RRMM treated with thalidomide-based regimens who previously received bortezomib and immunomodulatory agents (IMiDs), including thalidomide and lenalidomide. Results: In 47 patients with RRMM, the median age was 64 years and the median number of previous treatment lines, including bortezomib and IMiDs, was 3. Primary resistance to bortezomib and lenalidomide was observed in 12 (26%) and 8 (17%) patients, respectively. The most common regimen was a combination of thalidomide, cyclophosphamide, and dexamethasone. The overall response rate was 38%; 2 patients (4%) experienced a complete response, and 2 patients (4%) experienced a very good partial response. The overall response rate of patients previously exposed to thalidomide was 53%. The median progression-free survival was 5.9 months, and overall survival was 9.2 months. Patients with disease that responded to the thalidomide-based regimen had better progression-free survival compared to those who did not (median, 8.8 vs. 2.5 months; P = .008). The most common adverse events were anemia (51%) for hematologic toxicities and peripheral neuropathy (30%) for nonhematologic toxicities. Conclusion: Thalidomide-based regimens are potential salvage treatment options for patients with RRMM, even those with disease with prior resistance to IMiDs. For patients with multiple myeloma (MM) that relapsed after treatment with bortezomib- and lenalidomide-based regimens, there were no other treatment options in Korea until 2016. Thalidomide plus a dexamethasone-based regimen is one of the treatment options for patients with relapsed/refractory MM, even after treatment with prior immunomodulatory agents, including thalidomide and lenalidomide.