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.