Quantitative Analysis and Monitoring of EZH2 Mutations Using Liquid Biopsy in Follicular Lymphoma

Abstract

Recent advances in molecular technologies enable sensitive and quantitative assessment of circulating tumor DNA, offering a noninvasive disease monitoring tool for patients with malignant disorders. Here, we demonstrated on four follicular lymphoma cases that circulating tumor DNA based <i>EZH2</i> mutation analysis performed by a highly sensitive droplet digital PCR method may be a valuable treatment monitoring approach in <i>EZH2</i> mutant follicular lymphoma. <i>EZH2</i> variant allele frequencies changed in parallel with the volume of metabolically active tumor sites observed on 18F-fluorodeoxyglucose positron emission tomography combined with computer tomography (PET-CT) scans. Variant allele frequencies of <i>EZH2</i> mutations decreased or were eliminated rapidly upon successful treatment, with treatment failure being associated with elevated <i>EZH2</i> variant allele frequencies. We also demonstrated spatial heterogeneity in a patient with two different <i>EZH2</i> mutations in distinct anatomical sites, with both mutations simultaneously detected in the liquid biopsy specimen. In summary, circulating tumor DNA based <i>EZH2</i> mutation analysis offers a rapid, real-time, radiation-free monitoring tool for sensitive detection of <i>EZH2</i> mutations deriving from different anatomical sites in follicular lymphoma patients receiving immunochemotherapy.