Analysis of prognostic value of complete response by PET–CT and further stratification by clinical and biological markers in DLBCL patients

Positron emission tomography–computed tomography (PET–CT) is performed as the standard method for response assessment of diffuse large B cell lymphoma (DLBCL) patients. However, a substantial proportion of patients experience relapse even if they have achieved complete response (CR) defined by PET–CT. We validated the prognostic value of CR by PET–CT and applied the National Comprehensive Cancer Network-International Prognostic Index (NCCN–IPI) and cell of origin (COO) to patients with CR by PET–CT to evaluate their additional predictive ability for survival outcomes. We retrospectively analyzed DLBCL patients who were treated with R-CHOP or an R-CHOP-like regimen and who achieved CR by PET–CT or CT only. A total of 185 patients were analyzed: 114 patients achieved CR by PET–CT and 71 patients by CT only. Patients with CR by PET–CT had significantly better overall survival (OS) than those with CR by CT (5-year OS, 87.5 vs. 62.4%, P = 0.003). Patients with high risk according to the NCCN–IPI had a dismal outcome despite achieving CR by PET–CT (5-year OS, 61.8%). In contrast, low-, low-intermediate-, and high-intermediate-risk patients had excellent outcomes (5-year OS, 100, 89.7, and 93.5%, respectively). Among patients with CR by PET–CT, patients with germinal center B cell (GCB) DLBCL (n = 40) had significantly better survival than those with non-GCB DLBCL (n = 57) (5-year OS, 96.9 vs. 75.5%, P = 0.039). We demonstrated that CR by PET–CT was a better predictor of survival outcomes than CR by CT only. The NCCN–IPI and COO subtypes could identify a subpopulation of poor-risk patients among those who achieved CR by PET–CT.