Clinical Outcome of IgM Amyloidosis (AL) Following Stem Cell Transplantation.
Authors: Gertz Morie Abraham , Lacy Martha Q. , Dispenzieri Angela , Hayman Suzanne R. , Kumar Shaji K. , Ansell Stephen M. , Elliott Michelle A. , Gastineau Dennis A. , Inwards David J. , Johnston Patrick B. , Micallef Ivana N. , Porrata Luis F. , Litzow Mark R. 
Published: April 2020

Abstract
Introduction: The association of amyloidosis with immunoglobulin light chain disorders is well recognized. It is less commonly appreciated that amyloidosis can be associated with IgM monoclonal gammopathies. One of the available therapies for treating amyloidosis is stem cell transplantation. It is unknown whether the clinical outcomes in patients with IgM amyloidosis differs from those patients with light chain amyloidosis.
Patients: Among 242 amyloidosis patients receiving stem cell transplants 10 (4%) had an IgM monoclonal protein. Eight were Mλ. One was biclonal Mλ Mκ and one was biclonal Mκ Gλ. The age range was 56 to 71, median 64 years. Seven were men. The monoclonal protein ranged in size from 0.1 to 2.3 g/dL (median 1.2 g/dL). Patients were transplanted from 2 to 8 months (median 4 months) following histologic diagnosis of amyloid. The median time from the recognition of the IgM monoclonal protein to the diagnosis of amyloid was 1.3 months, but 2 patients, both of whom had overt Waldenström’s macroglobulinemia, were diagnosed 45 and 115 months respectively before amyloidosis developed. Of the cohort of 10, 3 fulfilled the criteria for symptomatic Waldenström’s macroglobulinemia.
Results: Amyloid syndromes were recognized in the kidney, heart, peripheral nerve and liver in 8, 3, 3 and 1 patient, respectively. Of the 3 peripheral neuropathy patients one also had autonomic failure. Seven of the 8 renal amyloid patients were confirmed with a renal biopsy. Their urinary protein loss ranged from 0.1 to 9.5 g/24h with a median of 4.7 g/24h. Six of the 10 patients had single organ involvement, 3 had 2 organ involvement and 1 had 3 organ involvement. All 3 Waldenström’s patients had prior exposure to cytotoxic chemotherapy. Amyloid deposits were seen in the bone marrow, fat and lymph node in 6, 5 and 1 patient, respectively. Patients underwent from 1 to 7 (median 3) apheresis with a median CD34 yield of 4.5 x 106/kg. Conditioning was Melphalan at 140 and 200 mg/m2 in 2 and 8 patients respectively. Neutrophil engraftment 500/μL occurred between day 11 and 30 (median 14) and for platelets 20,000/μL between day 11 and 406 (median day 16). The median number of hospitalization days ranged from 0 to 32 (median 12). Nine of the 10 patients fulfilled criteria for a hematologic response and to date 3 of these 9 have also achieved an organ response, including normalization of urinary protein loss in 2 nephrotic patients and a greater than 50% reduction in urinary protein loss in the third. None of the patients with amyloid neuropathy responded. One of the patients with cardiac amyloid showed echocardiographic evidence of improvement. At this time 8 survive and 2 died; 1 a treatment-related death (day +40) and 1 of relapse post transplant with progressive amyloid at 45 months. The median follow-up of surviving patients is 29 months.
Conclusion: The outcomes in patients with IgM amyloidosis following transplantation do not appear to be different from those with immunoglobulin light chain amyloidosis. There is no suggestion that the response rates are lower or that alternate conditioning schemes such as BEAM should be considered.