Tufts Medical Center, Boston, MA
Ping Zhou , Adin Kugelmass , Denis Toskic , Amandeep Godara , Teresa Fogaren , Cindy Varga , Ray Comenzo
Background: In systemic AL amyloidosis (AL), caused by clonal Ig free light chains (LC) produced in 75% of cases by λ clones, patients often present with advanced organ damage, making earlier diagnosis a critical unmet need. Five λIGLV germline genes account for 75% of AL λ-type (IGLV 6-57, 1-44, 2-14, 1-51, 3-1) (Blood 2017;129:299), representing 56% of all AL patients. Relative risk of AL versus MM with these clonal genes can be high (7.3, 6-57; 2.5, 1-44), intermediate (1.7, 2-14; 1.2, 1-51) or low (0.8, 3-1) (Amyloid 2009;16:1). Progression to AL from smoldering multiple myeloma (SMM) or monoclonal gammopathy of undetermined significance (MGUS) occurs but is not well appreciated (JCO 2014; 32:2679). SAVE is a trial for λ SMM or λ MGUS patients with a κ:λ FLC ratio < 0.26 and difference between involved and uninvolved FLC > 23mg/L (JCO 2014;32:2699). Methods: Eligible patients ship peripheral blood (PB) or bone marrow (BM) samples to us for RT-PCR with cDNA from CD138+ cells, using primers for the Vλ families (Blood 2001;98:714). Amplicons are sequenced and the IGLV germline genes identified in IMGT (ImMunoGene-Tics, www.imgt.org). If the germline gene is AL-related, further evaluation is pursued. Results: Twenty asymptomatic λ patients from 18 states have been enrolled (3M, 17F) and 23 PB and 4 BM specimens obtained. Medians of months from diagnosis, involved FLC, κ:λ ratios, MNC and CD138-selected cells were 20.5 months, 113mg/L, κ:λ 0.06, 8.1x106 (0.8-24) and 3x105 (0-30), respectively. Seventeen patients have had IGLV genes identified, 12 with the first and 5 with additional specimens including 4 BM. Increased risk of AL was identified in 7 patients, 2 of whom had undiagnosed AL (both with IGLV2-14 germline genes). One patient with SMM diagnosed in 2016 had AL λ-type with GI involvement and is 9 months status post MEL 200 stem cell transplant (SCT), and the second with SMM diagnosed in 2009 had cardiac AL λ-type by heart biopsy with an NT-proBNP 171 (but with a suggestive MRI) and is en route to SCT. Conclusions: The SAVE trial enables early diagnosis of AL λ-type based on the λIGLV gene used by the clonal plasma cells. By RT-PCR in this pilot study we identified the clonal λ gene 85% of the time. Earlier diagnosis will enable treatment with effective therapy such as MEL 200 SCT. Clinical trial information: NCT02741999
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