Date Published: March 22, 2019
Publisher: Public Library of Science
Author(s): Even H. Rustad, Malin Hultcrantz, Venkata D. Yellapantula, Theresia Akhlaghi, Caleb Ho, Maria E. Arcila, Mikhail Roshal, Akshar Patel, Denise Chen, Sean M. Devlin, Austin Jacobsen, Ying Huang, Jeffrey E. Miller, Elli Papaemmanuil, Ola Landgren, Noel F. C. C. de Miranda.
Tracking of clonal immunoglobulin V(D)J rearrangement sequences by next generation sequencing is highly sensitive for minimal residual disease in multiple myeloma. However, previous studies have found variable rates of V(D)J sequence identification at baseline, which could limit tracking. Here, we aimed to define the factors influencing the identification of clonal V(D)J sequences. Bone marrow mononuclear cells from 177 myeloma patients underwent V(D)J sequencing by the LymphoTrack assays (Invivoscribe). As a molecular control for tumor cell content, we sequenced the samples using our in-house myeloma panel myTYPE. V(D)J sequence clonality was identified in 81% of samples overall, as compared with 95% in samples where tumor-derived DNA was detectable by myTYPE. Clonality was detected more frequently in patients with lambda-restricted disease, mainly because of increased detection of kappa gene rearrangements. Finally, we describe how the tumor cell content of bone marrow aspirates decrease gradually in sequential pulls because of hemodilution: From the initial pull used for aspirate smear, to the final pull that is commonly used for research. In conclusion, baseline clonality detection rates of 95% or higher are feasible in multiple myeloma. Optimal performance depends on the use of good quality aspirates and/or subsequent tumor cell enrichment.
Achieving minimal residual disease (MRD) negativity after initial treatment for multiple myeloma is strongly associated with prolonged progression free (PFS) and overall survival (OS)[1–5]. Consequently, MRD testing is done in the vast majority of clinical trials, and it is gradually becoming standard of care. The clinical implications of MRD negativity are rapidly evolving as more sensitive methods are introduced. When MRD was first included in the IMWG response criteria for multiple myeloma in 2016, MRD negativity was defined as less than 1 tumor cell in 100 000 bone marrow cells (i.e. 10−5). Emerging evidence now shows prolonged PFS when raising the bar for MRD negativity to 10−6 (i.e. less than 1 tumor cell in 1 000 000 bone marrow cells), compared to the current IMWG definition [6–8].
MRD negativity after initial therapy is an important predictor of PFS and OS in patients with multiple myeloma [5–8]. Tracking of clonal V(D)J rearrangement sequences by NGS is highly sensitive and does not require immediate analysis of fresh samples by an expert laboratory [13–15]. Variable rates of identifying clonal V(D)J sequences at baseline remain a challenge for NGS-based assays, for reasons that are poorly understood. We show that clonality detection rates of at least 95% are feasible in multiple myeloma when the sample quality is good, and describe how disease biology and sample quality together influence the probability of clonality detection.