RecruitingDevice studyctDNA-guided Therapy Optimization in Newly Diagnosed DLBCLThe purpose of this study is to 1) determine whether it is feasible to measure circulating tumor DNA (ctDNA) in real-time during standard treatment for newly diagnosed diffuse large B-cell lymphoma (DLBCL), and 2) evaluate the outcomes of participants with undetectable ctDNA in the middle of treatment who receive a shortened course of chemotherapy. There are no investigational drug agents to be administered in this study. The investigational assay, phased variant enrichment and detection sequencing (PhasED-seq) will be used to guide de-escalation of standard-of-care therapy for newly diagnosed DLBCL. The PhasED-seq assay has not yet been approved by the Food and Drug Administration (FDA).