Measurement of Bone Marrow Tumour Burden and Minimal Residual Disease in Waldenstrom's Macroglobulinemia through Cell-free Whole Genome Sequencing

PurposeWe assessed the utility of blood cell-free DNA (cfDNA) whole genome sequencing (cfWGS) for minimal residual disease (MRD) monitoring in Waldenstroms macroglobulinemia (WM) by comparing this to 1) targeted panel sequencing of 27 genes of interest in WM and targeted capture of immunoglobulin gene rearrangements in blood and bone marrow 2) Multiplex-PCR of immunoglobulin loci followed by Illumina sequencing (clonoSEQ). Experimental designSamples were collected from 7 patients on a clinical trial who were treated uniformly with chemoimmunotherapy and Brutons Tyrosine Kinase inhibitor (BTKi). Samples were collected prior to starting treatment and at clinical timepoints up to 18 months. MRD detection technologies were compared across all timepoints. ResultscfWGS was superior to both in-house targeted panel sequencing on cfDNA and clinical NGS in peripheral blood (PB) cells, using clinical bone marrow (BM) NGS as a standard. Tumor burden measured by cfWGS reflected MRD counts by clonoSEQ in BM. ConclusionscfWGS may be a valuable non-invasive alternative to bone marrow testing in WM patients who require close follow up and provides greater sensitivity than targeted panel sequencing of cfDNA. Statement of Translational RelevanceWhole-genome sequencing in cell-free DNA (cfWGS) is a highly sensitive marker of minimal residual disease that has application as a biomarker in clinical trials. cfWGS more accurately reflects bone marrow tumor burden than other available non-invasive measures to date. Further exploration is warranted to determine its full potential for use in cancer diagnostics and research.