The best liquid biopsy for myeloma detection by immunoglobulin targeted NGS

Description

Objectives: Multiple myeloma (MM) is a spatially heterogeneous disease. Subclones at different locations may resist therapy while other lesions are in remission. Mutations conveying resistance can be missed if the relevant subclone isn’t present in the biopsy sample. New therapies have resulted in unprecedented response depths and necessitate novel, more sensitive criteria for remission. Currently, the best prognostic marker is the absence of measurable residual disease (MRD) after treatment. However, both detection of mutations and MRD necessitate (multiple) bone marrow biopsies. Moreover, due to the patchy distribution, residual disease or subclonal mutations may be missed. Liquid biopsies obtained by a simple blood draw may carry information which is more representative for the whole tumor mass. Both cell-free DNA (cfDNA) and circulating myeloma cells may be valid liquid biopsy specimen.Methods: To study the feasibility and accuracy of myeloma derived DNA detection in liquid biopsies, paired bone marrow (BM) and peripheral blood samples from 44 myeloma patients with a newly diagnosed or relapsed/refractory myeloma were collected. For 4 patients, samples were collected at two different time points. Plasma was separated through centrifugation, peripheral blood mononuclear cells (PBMNCs) were separated by ficoll density gradient centrifugation. Subsequently, circulating tumor cells (CTCs) were immunomagnetically enriched based on CD138 expression. DNA was extracted from all samples and tumor DNA was detected through immunoglobulin (IG) targeted next-generation sequencing (NGS).Results: At least one clonal IG-sequence could be detected in BM DNA of 41 out of 44 patients (93%): a clonal IGH and IGK rearrangement was found in 66% and 77% of cases, respectively while both rearrangements were detected in 23/44 patients (52%). Average plasma cell concentrations on smears of BM samples where NGS could detect a clonal sequence was 23% (3%-80%). Forty paired BM and cfDNA samples of 37 patients were available for analysis. The clonal MM sequence found in the BM, could be detected in 31 of 40 cfDNA samples (78%). For 34 samples collected from 33 patients, PBMNCs and enriched CTCs were also analyzed. The clonal MM sequences found in the BM could be detected in 30/34 (88%) of PBMNCs samples and all enriched CTCs samples. CD138-enriched CTCs were significantly better for tumor detection than cfDNA (p<0.005). Pseudoclonality due to low DNA input for NGS was more often observed in cfDNA samples (50%) compared to enriched CTCs samples (7%).Conclusion: In summary, our findings indicate that tumor DNA is present in CD138-enriched CTCs of myeloma patients at diagnosis or relapse. This suggest that the presence of tumor DNA and mutational information could be derived from a simple blood draw in myeloma patients with active disease, allowing to obtain integrated biological and prognostic information at diagnosis and during follow-up.

Period	4 Feb 2022
Event title	37th General Annual Meeting of the Belgian Hematology Society
Event type	Conference
Location	La Hulpe, Belgium
Degree of Recognition	National