Interlaboratory Analytical Validation of a Next-Generation Sequencing Strategy for Clonotypic Assessment and Minimal Residual Disease Monitoring in Multiple Myeloma

Context.-Minimal residual disease (MRD) is a major prognostic factor in multiple myeloma, although validated technologies are limited. Objective.-To standardize the performance of the LymphoTrack next-generation sequencing (NGS) assays (Invivoscribe), targeting clonal immunoglobulin rearrangements, in order to reproduce the detection of tumor clonotypes and MRD quantitation in myeloma. Design.-The quantification ability of the assay was evaluated through serial dilution experiments. Paired samples from 101 patients were tested by LymphoTrack, using Sanger sequencing and EuroFlow's next-generation flow (NGF) assay as validated references for diagnostic and follow-up evaluation, respectively. MRD studies using LymphoTrack were performed in parallel at 2 laboratories to evaluate reproducibility. Results.-Sensitivity was set as 1.3 tumor cells per total number of input cells. Clonality was confirmed in 99% and 100% of cases with Sanger and NGS, respectively, showing great concordance (97.9%), although several samples had minor discordances in the nucleotide sequence of rearrangements. Parallel NGS was performed in 82 follow-up cases, achieving a median sensitivity of 0.001%, while for NGF, median sensitivity was 0.0002%. Reproducibility of LymphoTrack-based MRD studies (85.4%) and correlation with NGF (R-2 > 0.800) were high. Bland-Altman tests showed highly significant levels of agreement between flow and sequencing. Conclusions.-Taken together, we have shown that LymphoTrack is a suitable strategy for clonality detection and MRD evaluation, with results comparable to gold standard procedures.