NGS-Based Molecular Karyotyping of Multiple Myeloma: Results from the GEM12 Clinical Trial

Imaging flow cytometric detection of del(17p) in bone marrow and circulating plasma cells in multiple myeloma

BACKGROUND

Detection of del(17p) in myeloma is generally performed by fluorescence in situ hybridization (FISH) on a slide with analysis of up to 200 nuclei. The small cell sample analyzed makes this a low precision test. We report the utility of an automated FISH method, called "immuno-flowFISH", to detect plasma cells with adverse prognostic risk del(17p) in bone marrow and blood samples of patients with myeloma.

METHODS

Bone marrow (n = 31) and blood (n = 19) samples from 35 patients with myeloma were analyzed using immuno-flowFISH. Plasma cells were identified by CD38/CD138-immunophenotypic gating and assessed for the 17p locus and centromere of chromosome 17. Cells were acquired on an AMNIS ImageStreamX MkII imaging flow cytometer using INSPIRE software.

RESULTS

Chromosome 17 abnormalities were identified in CD38/CD138-positive cells in bone marrow (6/31) and blood (4/19) samples when the percent plasma cell burden ranged from 0.03% to 100% of cells. Abnormalities could be identified in 14.5%-100% of plasma cells.

CONCLUSIONS

The "immuno-flowFISH" imaging flow cytometric method could detect del(17p) in plasma cells in both bone marrow and blood samples of myeloma patients. This method was also able to detect gains and losses of chromosome 17, which are also of prognostic significance. The lowest levels of 0.009% (bone marrow) and 0.001% (blood) for chromosome 17 abnormalities was below the detection limit of current FISH method. This method offers potential as a new means of identifying these prognostically important chromosomal defects, even when only rare cells are present and for serial disease monitoring.

Cytogenetics in the management of multiple Myeloma: The guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Multiple myeloma (MM) is characterized by the accumulation of malignant plasma cells (PCs) in the bone marrow. Despite considerable advances in the treatment, MM is considered an incurable chronic disease with a very heterogeneous prognosis, mostly depending on genomic alterations whose complexity evolves over time. The cytogenetic analysis of MM is performed on CD138+ sorted PCs, in order to detect the following high risk cytogenetic abnormalities: t(4;14), 17p/TP53 deletion, 1q21 gain/amplification, 1p32 deletion, as well as t(11;14) because of its therapeutic implication. This minimal panel can be enlarged to detect other recurrent abnormalities, according to the prognostic score chosen by the laboratory. Although the knowledge of the genetic landscape of MM is evolving rapidly with improved molecular technologies, risk scores remain to be refined as they require more time for consensual validation. The GFCH present here the overview of genomics alterations identified in MM and related PCs diseases associated with their prognostic factor, when available, and recommendations from an expert group for identification and characterization of those alterations. This work is the update of previous 2016 recommendations.

Identification of Immunoglobulin Gene Rearrangement Biomarkers in Multiple Myeloma through cfDNA-Based Liquid Biopsy Using tchDNA-Seq

Multiple myeloma (MM) is a hematological malignancy characterized by the clonal proliferation of pathogenic CD138+ plasma cells (PPCs) in bone marrow (BM). Recent years have seen a significant increase in the treatment options for MM; however, most patients who achieve complete the response ultimately relapse. The earlier detection of tumor-related clonal DNA would thus be very beneficial for patients with MM and would enable timely therapeutic interventions to improve outcomes. Liquid biopsy of "cell-free DNA" (cfDNA) as a minimally invasive approach might be more effective than BM aspiration not only for the diagnosis but also for the detection of early recurrence. Most studies thus far have addressed the comparative quantification of patient-specific biomarkers in cfDNA with PPCs and BM samples, which have shown good correlations. However, there are limitations to this approach, such as the difficulty in obtaining enough circulating free tumor DNA to achieve sufficient sensitivity for the assessment of minimal residual disease. Herein, we summarize current data on methodologies to characterize MM, and we present evidence that targeted capture hybridization DNA sequencing (tchDNA-Seq) can provide robust biomarkers in cfDNA, including immunoglobulin (IG) rearrangements. We also show that detection can be improved by prior purification of the cfDNA. Overall, liquid biopsies of cfDNA to monitor IG rearrangements have the potential to provide important diagnostic, prognostic, and predictive information in patients with MM.