LAUSR

The sensitivity of conventional techniques for reliable quantification of minimal/measurable residual disease (MRD) in chronic lymphocytic leukemia (CLL) is limited to MRD 10-4. Measuring MRD <10-4 could help to further distinguish between CLL patients with durable remission and those at risk of early relapse. We here present an academically developed IGHV leader-based next-generation sequencing (NGS) assay for the quantification of MRD in CLL. We demonstrate, based on measurements in contrived MRD samples, that the linear range of detection and quantification of our assay reaches beyond MRD 10-5. If provided with sufficient DNA input, MRD can be detected down to MRD 10-6. There was high inter-assay concordance between measurements of the IGHV leader-based NGS assay and allele-specific oligonucleotide quantitative PCR (r=0.92, [95%CI 0.86-0.96]) and droplet digital PCR (r=0.93, [95%CI 0.88-0.96]) on contrived MRD samples. In a cohort of 67 patients from the CLL11 trial, using MRD 10-5 as a cut-off, undetectable MRD was associated with superior progression-free survival (PFS) and time to next treatment. Importantly, deeper MRD measurement allowed for additional stratification of patients with MRD <10-4 but ≥10‑5. PFS of patients in this MRD range was significantly shorter, compared to patients with MRD <10-5 (HR 4.0, [95%CI 1.6-10.3], P=0.004), but significantly longer, compared to patients with MRD ≥10‑4 (HR 0.44, [95%CI 0.23-0.87], P=0.018). These results support the clinical utility of the IGHV leader-based NGS assay.