(A-D) PFS and OS analysis of stage IV patients, by marrow status. PFS and OS of cases identified by (A-B) PET-CT (PET) or (C-D) marrow biopsy (BMB) histology. Marrow PET-positive cases had outcomes similar to marrow PET-negative stage IV cases. Cases with DLBCL cells identified in marrow histologically had inferior survivals (P < .01). The number of cases in each group, and at risk at each follow up time point, are shown.