In a new study, researchers described an assay developed for measuring minimal residual disease (MRD) in patients with lymphoma involving the central nervous system (CNS). The MRD assay is based on next-generation sequencing (NGS) of tumor-derived DNA detected in cerebrospinal fluid (CSF) and is aimed at identifying clonotypic immunoglobulin gene rearrangements. Results of the study were published in the journal Blood Advances.
The study was based at Rhode Island Hospital in Providence, Rhode Island, and it involved analyzing DNA from 3 groups of patients for clonotypic, tumor-specific DNA rearrangements. Group 1 included 7 patients with primary or secondary CNS lymphoma from whom CSF had been collected prospectively. Group 2 included 8 patients with CNS involvement for whom stored CSF samples were available for retrospective analysis. Group 3 was an observational group that included 22 patients with newly diagnosed aggressive lymphomas without known CNS involvement, but who were considered to be at high risk for CNS relapse.
Samples were obtained from groups 1 and 2 at the time of diagnostic procedures, and from group 3 prior to receipt of intrathecal therapy or high-dose methotrexate. Groups 1 and 2 were analyzed for diagnostic utility of the assay, and group 3 was analyzed prognostically. The NGS-MRD assay examined cell-free and genomic DNA and targeted portions of IGH, IGK, and IGL loci for sequencing.
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The NGS-MRD assay identified clonotypic DNA in all 7 patients in group 1. There were 2 of these patients who had shown lymphomas only in brain parenchyma and with otherwise negative results in other CSF-based analyses of cytology, flow cytometry, or PCR of IGH. Leptomeningeal disease was associated with a higher cell-free DNA median copy number in the CSF than was seen with parenchymal-only disease (1649 versus 2.0 copies/mL; P =.04). Some results from group 2 appeared to reflect discrepancies in handling of the previously obtained samples, although 6 patients had detectable clonotypic DNA using the NGS-MRD assay.
Among the patients in group 3 who had aggressive lymphomas without known CNS involvement, 91% had received CNS prophylaxis following enrollment. More than one-third (36%) of the patients in group 3 showed positive results using the NGS-MRD assay described in this study. A positive result using this assay was linked to a 12-month cumulative risk of CNS recurrence of 28.6%, in comparison with 0% for a negative result at baseline (P =.045).
“These data lay the groundwork for novel approaches to highly sensitive molecular CSF evaluations, including a more accurate selection of patients for CNS-directed prophylaxis,” the study investigators wrote in their report.
Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.
Reference
Olszewski AJ, Chorzalska AD, Petersen M, et al. Detection of clonotypic DNA in the cerebrospinal fluid as a marker of central nervous system invasion in lymphoma. Blood Adv. 2021;5(24):5525-5535. doi:10.1182/bloodadvances.2021004512
