Thalidomide treatment for patients with previously untreated multiple myeloma: a meta-analysis of randomized controlled trials

The efficacy and safety of thalidomide as an initial treatment in myeloma patients who were unsuitable for autologous stem cell transplantation (ASCT), as induction treatment prior to ASCT, or as a maintenance treatment was unclear. The purpose of this study was to assess the benefits and risks of thalidomide for previously untreated myeloma patients. MEDLINE, EMBASE, and Cochrane Library were searched for randomized controlled trials (RCTs) of thalidomide used in either induction or maintenance therapy for previously untreated myeloma patients. Twenty-two RCTs enrolling 9098 patients were identified, including 15 RCTs of induction thalidomide, 6 RCTs of maintenance thalidomide, and 1 RCT of induction and maintenance thalidomide. Induction thalidomide improved overall response rate (ORR) (risk ratio (RR) 1.54, 95 % confidence interval (CI) 1.30–1.83), complete response rate (CRR) (RR 3.03, 95 % CI 1.91–4.80), progression-free survival (PFS) (hazard ratio (HR) 0.65, 95 % CI 0.56–0.76), and overall survival (OS) (HR 0.78, 95 % CI 0.67–0.91) in patients who were not allowed to receive ASCT. Induction thalidomide improved pre-ASCT ORR (RR 1.20, 95 % CI 1.11–1.30), pre-ASCT and post-ASCT CRR (RR 1.47, 95 % CI 1.12–1.93 and RR 1.23, 95 % CI 1.00–1.50, respectively), and PFS (HR 0.73, 95 % CI 0.59–0.91) in patients who were allowed to receive ASCT, but it did not improve post-ASCT ORR (RR 1.04, 95 % CI 0.99–1.09) and OS (HR 0.91, 95 % CI 0.79–1.05). Improved PFS and prolonged OS were observed (HR 0.61, 95 % CI 0.53–0.70 and HR 0.77, 95 % CI 0.62–0.95, respectively) when thalidomide was added to maintenance therapy. More patients experienced venous thromboembolism (VTE) of grade 3/4 when thalidomide was added to induction or maintenance therapy (HR 2.15, 95 % CI 1.58–2.92 and RR 1.96, 95 % CI 1.13–3.40, respectively). Induction thalidomide still increased the risk of VTE (RR 1.53, 95 % CI 1.12–2.08) after VTE prophylaxis was used. Induction thalidomide effectively improved CRR, ORR, and PFS (except post-ASCT ORR). Notably, induction thalidomide improved OS in patients who were not allowed to receive ASCT but not in patients who were allowed to receive ASCT. The addition of thalidomide to maintenance therapy improved both PFS and OS. However, thalidomide led to a greater risk of VTE with grade 3/4. This risk did not disappear after VTE prophylaxis was used in induction therapy with thalidomide.