Second Stem Cell Transplantation for Relapsed Refractory Light Chain (AL) Amyloidosis

Autologous stem cell transplantation (ASCT) is an effective treatment modality in light chain (AL) amyloidosis but can be offered only to a subset of patients. The feasibility, benefit, and risks of second ASCT (ASCT2) have been rarely reported. The objective of this study was to assess the utility of ASCT2 in AL amyloidosis and to identify the target population with the greatest benefit. This retrospective study examined all AL patients who underwent ASCT2 for relapsed refractory disease between 2003 and 2020. Twenty-six patients were included. The use of ASCT2 has increased over time, from 2.5% of all ASCTs from 2003 to 2011 to 5% from 2012 to 2020 (P = .056). The median time between the first ASCT (ASCT1) and ASCT2 was 7.2 years (range, 0.6 to 17.7). Fifty-four percent of patients received at least one line of therapy between ASCTs. Second stem cell mobilization prior to ASCT2 was required in 42% of patients. Full-dose melphalan (200 mg/m²) was given to 73% of patients. Two patients had failed to engraft by day 100 but eventually recovered to normal blood counts. Both had second stem cell mobilization prior to ASCT2 with prior melphalan exposure. Four patients (15%) died before day 100. Progression-free and overall survival were significantly longer from ASCT2 for those who had durable remission after ASCT1 (≥5 years) and for those who did not receive therapy between ASCTs. ASCT2 is feasible and can produce favorable outcomes, especially among those with durable response to ASCT1. ASCT2, if chosen, should preferably be performed after durable response to ASCT1 and at first progression.