Impact of second autologous stem-cell transplantation at relapsed multiple myeloma: A French multicentric real-life study

A second autologous stem-cell transplantation (ASCT2) is considered for relapsed multiple myeloma (RMM) patients showing prolonged response after a first ASCT. However, given breakthrough treatments like anti-CD38 and immunotherapy, its role remains debated. We conducted a real-life study in 10 French centers (1996–2017) involving 267 RMM patients receiving ASCT2. The median age was 61 years, with 49% females. Most patients received melphalan 200 mg/m² before ASCT2, with low early mortality (1%). Very good partial response or better (VGPR+) rate post ASCT2 was 78%. Post ASCT2, 48% received consolidation therapy and 40% maintenance therapy. Median event-free survival (EFS) after ASCT2 was 2.6 years (95% confidence interval [CI]: 2.3–2.8), and 2-year EFS estimate was 63% (95% CI: 57–70). Median overall survival (OS) was 8.1 years (95% CI: 5.9–NA), and 2-year OS estimate was 92% (95% CI: 88–95). Multivariate analysis revealed that VGPR+ status and maintenance therapy post ASCT2 were associated with better EFS (hazard ratio [HR]: 0.6; 95% CI: 0.3–0.9, p = 0.012 and HR: 0.4; 95% CI: 0.3–0.6, p < 0.001, respectively) and OS (HR: 0.4; 95% CI: 0.2–0.9, p = 0.017 and HR: 0.2; 95% CI: 0.1–0.4, p < 0.001, respectively), while male sex correlated with poorer outcomes for EFS (HR: 2.5; 95% CI: 1.7–3.7, p < 0.001) and OS (HR: 2.7; 95% CI: 1.4–4.9, p = 0.002). Overall, ASCT2 appeared efficient with low toxicity in RMM. Maintenance therapy was associated with extended EFS and OS, particularly in patients with VGPR+ status post ASCT2. These findings underscore ASCT2's potential in RMM when coupled with maintenance therapy in selected patients.