Molecular Monitoring With Circulating Tumor DNA and Nivolumab Maintenance

Primary Objective: To determine if nivolumab administration, as a maintenance strategy in DLBCL patients with high risk of relapse, can convert positive ctDNA to negative ctDNA and/or result in relapse free survival (RFS-ctDNA) of 9 months or longer after positive ctDNA was documented. Secondary Objectives: 1. To evaluate safety of nivolumab as maintenance drug in post-induction, post-salvage and post-autologous transplant setting 2. Relapse free survival (RFS-ctDNA) for nivolumab treated patients 3. Proportion of patients who are able to convert from ctDNA positive to ctDNA negative after nivolumab treatment 4. To validate NeoLabs assay platform by comparing the results to Clonoseq platform.