Limited benefits of thalidomide and dexamethasone maintenance after autologous stem cell transplantation in newly diagnosed multiple myeloma patients: a prospective phase II multi-center study in Korea

Although the clinical outcome of newly diagnosed multiple myeloma has improved with maintenance therapy, maintenance with novel agents is not always available depending on medical expenses or drug accessibility. We intended to investigate the efficacy and toxicity of thalidomide/dexamethasone maintenance in Korean patients. In this multicenter phase 2 study, patients with newly diagnosed myeloma who underwent induction chemotherapy followed by autologous stem cell transplantation (ASCT) were enrolled to receive maintenance treatment of 100mg thalidomide daily for 28 days and 40mg dexamethasone daily for 4 days each cycle. Maintenance was given up to 12 cycles. The primary endpoint was a 1-year event free survival (EFS) rate. It was assumed that EFS at 1-year would be 91% with thalidomide and 1-year EFS below 82% would be of no effect. A total of 43 patients were consecutively enrolled (median age, 58 years [range, 34 – 65]; male, n = 31). With a median follow-up duration of 17.3 months (range, 1.1 – 32.2), EFS at 1 year was 65.1% (95% confidence interval [CI], 48.9 – 77.3). PFS and OS at 1 year was 85.6% (95% CI, 70.7 – 93.3) and 90.4 (95% CI, 76.3 – 96.3), respectively. In terms of side effects, 39 patients (90.7%) experienced adverse events (AEs) of any grade, and 14 patients (32.6%) experienced grade 3 or 4 adverse events. 15 patients (34.9%) failed to complete 12 cycles of maintenance, and the most common reason for premature termination was AEs (n = 6). In Korean patients the benefits of thalidomide maintenance does not seem to outweigh the toxicity of thalidomide, especially in high-risk MM. Considering the long clinical course of MM, preservation of quality of life and finances might be more beneficial for subsequent MM treatment.