Comparative Study of Circulating Tumor DNA and Computerized Tomography Monitoring in Untreated Diffuse Large B-Cell Lymphoma

Background— Diffuse large-B-cell lymphoma (DLBCL) is curable but when treatment fails, outcome is poor. Imaging scans help identify patients at risk of treatment failure but are often imprecise, and the radiation exposure is a potential health risk. Specific, sensitive and readily available biomarkers of treatment failure are needed. Methods— We retrospectively analyzed cell-free circulating tumor DNA (ctDNA) in patients treated on one of 3 treatment protocols using quantitative next-generation DNA sequencing. Eligible patients had DLBCL, no evidence of indolent lymphoma and were previously untreated. Serial serum samples and concurrent computed tomography scans were obtained at specified times during most treatment cycles and 5-years of follow-up. VDJ gene segments of the rearranged immunoglobulin receptor genes were amplified and sequenced from pre-treatment specimens and serum ctDNA encoding the VDJ rearrangements was quantitated. Findings— Tumor clonotype(s) were identified in pretreatment specimens from 126 patients who were followed for a median (interquartile range) of 11 (6.8 to 14.2) years. Interim ctDNA monitoring at the end of 2 treatment cycles in 108 patients showed a time to progression (TTP) of 41.7% (95% Confidence Interval (CI): 22.2% to 60.1%) and 80.2% (95% CI: 69.6% to 87.3%), at 5-years (p<0.0001) in patients with and without detectable ctDNA, respectively, and a positive and negative predicative value (PPV and NPV) of 63% and 80%, respectively. Surveillance ctDNA monitoring was performed in 107 patients who achieved complete remission. A Cox proportional hazards model showed patients who developed detectable ctDNA during surveillance had a hazard ratio 228 times that of patients with undetectable ctDNA for clinical disease progression (95% CI: 51 to 1022) (p<0.0001). Surveillance ctDNA had a PPV and NPV of 88% and 98%, respectively, and identified recurrence a median (range) of 3.5 months (0 to 200) before evidence of clinical disease. Interpretation— Surveillance ctDNA identifies patients at risk of recurrence before clinical evidence of disease in most patients and results in lower disease burden at relapse. Interim ctDNA is a promising biomarker to identify patients at high risk of treatment failure. Kruskal-Wallis test was used. Sensitivity, specificity, and positive and negative predictive (PPV and NPV) of ctDNA detection of clinical disease were calculated based on the final determinations of ctDNA and clinical progression or not as dichotomous outcomes. 27 All p-values are two-tailed. Statistical analyses were performed using SAS version 9.3 and Prism version 6.0. illustrates following is Two patients (#35, single low-level positive ctDNA during surveillance and did not have clinical progression. samples time points were reanalyzed both and were negative ctDNA the suggesting these were false