JCO Article Insights: ctDNA in DLBCL - Ready for Prime Time?

In this episode of JCO Article Insights, host Dr.  Ash Gurumurthi summarizes JCO articles, "Phased Variant–Supported Circulating Tumor DNA as a Prognostic Biomarker After First-Line Treatment in Large B-Cell Lymphoma: Findings From the DIRECT Study" and " Prospective Validation of Circulating Tumor DNA Measurable Residual Disease After First-Line Therapy in Large B-Cell Lymphoma" TRANSCRIPT Ash Gurumurthi: Hi and welcome to JCO Article Insights. I'm your host, Ash Gurumurthi, and today we will be discussing two articles, both published in the Journal of Clinical Oncology, on the real-world utility of circulating tumor DNA (ctDNA) MRD in newly diagnosed large B-cell lymphoma. The first study is the article "Phased-Variant-Supported Circulating Tumor DNA as a Prognostic Biomarker After First-Line Treatment in Large B-Cell Lymphoma: Findings From the DIRECT Study" by Dr. Joanna Krupka and colleagues in the United Kingdom. For the sake of convenience, I'll refer to this as the DIRECT study. The second study is "The Prospective Validation of Circulating Tumor DNA Measurable Residual Disease After First-Line Therapy in Large B-Cell Lymphoma" by Dr. Steven Wang and colleagues in the Netherlands, referred to as the HOVON 902 study. By way of background, I wanted to talk about MRD in hematolymphoid malignancies. Nodal diseases have lacked a robust biomarker for end-of-treatment response. They have relied historically on PET scans interpreted using the semiquantitative Deauville 5-point scale, which has a high negative predictive value but a limited positive predictive value. The poor positive predictive value for survival results in extended follow-up with serial imaging for risk stratification with unnecessary and invasive biopsies. There have been recent revolutionary advancements in ctDNA MRD in B-cell lymphoma. The use of ctDNA in lymphoma began with CAPP-seq, which tracked single nucleotide variants that were tumor specific but was limited by excessive background sequencing noise with false negatives. To overcome this, Dr. Kurtz and colleagues developed the proprietary PhasED-seq assay. This tracks well-recognized phased mutations on the same DNA strand in cis configuration within hypermutated regions that are unique to B-cell lymphoma. Using this method, they pushed their limit of detection at 95%, the so-called LOD95, to 0.7 parts per million under optimal circumstances with 120 nanograms of input cell-free DNA from plasma. Based on the use of the PhasED-seq assay in trials of newly diagnosed large B-cell lymphoma with the use of investigational agents, the NCCN currently recommends consideration of ctDNA MRD assay with a detection limit of less than 1 part per million if biopsy is not feasible for a positive end-of-treatment PET. However, I believe this threshold needs reconsideration given it is based on an ideal assay LOD95 under optimal circumstances rather than sample-specific LOD95. Real-world validation of the role of end-of-treatment ctDNA and appropriate thresholds for sample-specific