Inclusion Criteria:  (1) pathologically proven DLBCL, (2) first-line treatment with R-CHOP or R-CHOP-like chemotherapy including R-miniCHOP and R-ECHOP (rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin),(3) at least 2 evaluable hypermetabolic lesions on PET/CT, (4) underwent pre-treatment [18F]FDG PET/CT  Exclusion Criteria:  (1) patients who had received surgical resection or other treatments before chemotherapy, (2) patients who had coexistent central system lymphoma or other types of malignancies