Light Chain Deposition Disease: Impact of Stem Cell Tranplant on Hematological Response Achievement.
Authors: Jimenez-Zepeda Victor H , Franke Norman , Winter Andrew , Reece Donna E. , Trudel Suzanne , Chen Christine , Rabea Ahmed M. , Kukreti Vishal 
Published: October 2019

Abstract
Abstract 4600
Light chain deposition disease (LCDD) is a systemic disorder characterized by deposition of monoclonal light chains (LC) in different organs. A single clone of plasma cells is responsible for the overproduction of either kappa or rarely lambda LC. Renal dysfunction generally is the main feature but many organs could be affected. The treatment of LCDD has not been standardized and remains controversial because of the small number of patients reported in the literature. However, as LCDD is associated with plasma cell dyscrasias, patients have typically been treated with regimens used for multiple myeloma, most commonly melphalan (mel) and prednisone and VAD (Vincristine, Adriamycin and Dexamethasone). Here, we report our experience using High Dose Melphalan (HDM) with Autologous Stem Cell Transplant (ASCT) in five patients (pts) with LCDD. In addition, we report the use of Velcade (vel) as induction therapy in two patients before undergoing ASCT.

Patients and Methods
We retrospectively reviewed the records of all pts treated with HDM/ASCT at Princess Margaret Hospital between January 2004 and December 2009 and identified five pts with LCDD. Pretreatment evaluation included staging investigations: 1) complete blood cell counts, 2) complete biochemistry panel, 3) albumin and β2-microglobulin, 4) Blood and Urinary Monoclonal protein assessment including Free LC Assay; 5) skeletal survey. 6) Bone marrow aspirate and biopsy. Pts with LCDD and concurrent multiple myeloma were excluded. LCDD was diagnosed by renal biopsy in all pts with histology confirming characteristic linear monoclonal LC deposits along the tubular membrane staining for kappa and lambda chains on inmunofluorescence. All pts received induction therapy prior to consolidation with HDM/ASCT [dexamethasone (n=3) and vel plus dexamethasone (n=2)]. Assessment of hematologic response (HR) to treatment was based on modified EORTC consensus criteria.

Results
Pts characteristics are shown in Table 1. Two pts were male subjects; the median age was 55 (range 45–65). All five pts, had elevated serum FLC and an abnormal κ-to- λ ratio. All of the pts presented with kidney involvement. The monoclonal protein deposited in the kidney consisted of free κ-LC in four pts and free lambda LC in 1. Two pts received vel and dexamethasone (3 cycles) induction therapy achieving PR after 6 weeks of therapy and three received dexamethasone alone: 1 pt achieving a PR and 2 SD. All of them received a conditioning regimen of mel 200 mg/m2. Complete HR was seen in 3 pts and PR in 1 patient (ORR 80%, CR 60%). Transplanted pts had a median time to ANC ≥0.5 ×109/L of 12d (Range 12–13) and time to platelets ≥ 20 ×109/L was 14 days (Range 12–17). Median time to discharge was 17 days (range 13–30) and no pts exhibited engraftment syndrome. There was no mortality related to transplant. The most common grade 3/4 adverse events included: neutropenic fever (n=5); mucositis (n=2); and transient worsening in kidney function (n=1). All pts are alive and progression-free at a median follow-up of 20 months (range 7–37) from transplant. As kidney dysfunction represents the most prominent morbidity in LCDD, it is important to emphasize that the elevated serum creatinine was ameliorated in these pts after ASCT

Conclusions
LCDD is a rare condition and its management is controversial. In a few small series, investigators have reported that high-dose melphalan (HDM) followed by ASCT can be associated with beneficial results whereas toxicity remains acceptable in this group of pts. We report our experience using HDM and ASCT in pts with LCDD without concurrent myeloma, demonstrating feasibility and tolerability.

Disclosures:
Reece: Celgene: Honoraria, Research Funding. Chen:Celgene Corporation: Consultancy, Honoraria, Research Funding. Kukreti:Celgene: Honoraria.