Factors Influencing the Outcome of a Second Autologous Stem Cell Transplant (ASCT) in Relapsed Multiple Myeloma: A Study from the British Society of Blood and Marrow Transplantation Registry

Autologous stem cell transplant as primary (first ASCT) therapy in multiple myeloma (MM) is standard practice. The role of a second ASCT as management of relapsed disease remains uncertain. We conducted a retrospective case-matched control analysis on patients (n = 106) who underwent a second ASCT compared with conventional chemotherapy (CCT) as for relapsed MM. The median age was 53 years (range: 26-75) and median follow-up 48 months (range: 8, 136). The cumulative incidence of 1 and 5 years nonrelapse mortality (NRM) was 7% (95% confidence interval [CI] 3%-13%) and 12% (95% CI 7%-19%), with a second ASCT inducing a greater partial remission (PR) rate of 63%. The 4-year overall survival (OS) rate was 33% (95% CI 24%-45%). Factors associated with improved OS and progression-free survival (PFS) included younger age (<55 years), β2MG <2.5 mg/L at diagnosis, a remission duration of >9 months from first ASCT, and a greater PR in response to their first ASCT. In a matched-cohort analysis with patients receiving conventional chemotherapy (CCT), the same factors were associated with improved OS, with the exception of a longer remission duration (>18 months) from first ASCT. Second ASCT in relapsed MM is associated with superior OS and PFS compared with CCT, offering a potential consolidative option for selected patients.