Impact of Bone Marrow Plasmacytosis on Outcome in Patients with AL Amyloidosis Following Autologous Stem Cell Transplant

Background: Previous studies have demonstrated inferior overall survival (OS) among patients with AL amyloidosis who have bone marrow plasmacytosis (BMPC) >10%. It is well recognized that AL patients who achieve the deepest hematologic responses have superior organ response and OS rate.

Methods: We designed a study to determine if BMPC% affects CR rate post ASCT and whether pre-transplant induction therapy improves response rate and OS among patients with a higher baseline BMPC burden.

Results: Among 415 AL patients who underwent ASCT at Mayo Clinic, Rochester within 12 months of diagnosis, 116 (28%) had BMPC>10% at diagnosis. The median age was 57.2 years. The median follow up for surviving patients was 67.3 months. There was no statistically significant difference in age, gender, time from diagnosis to transplant, or use of attenuated conditioning regimen between groups with high (>10%) and low (≤ 10%) bone marrow involvement. The high BMPC group tended to receive more induction chemotherapy before ASCT, and presented with greater value of albumin, beta-2 microglobulin and difference in serum free light chain (dFLC). A higher CR rate was observed in low BMPC group (44.6% versus 26.7%, p=0.0013). In patients with high BMPC, a higher CR rate (33.9% versus 17.7%, p<0.05) was seen in those who received pre-ASCT induction therapy compared with no induction therapy. Among 3 groups of patients who had: no pre-ASCT therapy; steroid only as induction; and induction chemotherapy, the 5-year OS rates were 50.5%, 40% & 67.5%, respectively, p<0.03.

Conclusions: Lower bone marrow burden at diagnosis yielded a deeper response following ASCT. Compared to no therapy, patients who were treated with steroid only pre-ASCT had an inferior OS, but other induction regimens appeared to improve survival. These data would support the concept that using induction therapy prior to ASCT conditioning among patients with higher tumor burden may be of value.

Figure 1. In BMPC > 10% at diagnosis, OS comparison between induction therapies pre-ASCT