Prognostic value of negative interim 2-[18F]-fluoro-2-deoxy-d-glucose PET/CT in diffuse large B-cell lymphoma

• About 39% of patients showed progression after negative interim PET/CT.
• The IPI score was an independent predictor for PFS.
• It is important to closely follow-up with high IPI score patients, even their negative interim PET.

AimTo assess the prognostic value of negative interim combined 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) positron-emission tomography/computed tomography (PET/CT) in patients with diffuse large B-cell lymphoma (DLBCL).Materials and methodsNinety-two patients with histologically proven DLBCL were enrolled. All of the patients underwent 18F-FDG PET/CT at diagnosis, and interim PET/CT after the second cycle of chemotherapy with rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisolone (R-CHOP). Negative interim PET/CT was defined as the disappearance of all abnormal 18F-FDG uptake compared to the pretreatment PET/CT image, as determined by visual assessment. The clinical outcome of patients was estimated as progression-free survival (PFS), and the prognostic significance of clinicopathological and imaging parameters were assessed using the Cox proportional hazards model.ResultsThirty-six patients (39.1%) showed lymphoma progression within a median follow-up of 30.8 months. According to univariate analysis, Ann Arbor stage, serum lactate dehydrogenase level, Eastern Cooperative Oncology Group scale, International Prognostic Index (IPI) score, and maximum standardised uptake values on initial PET/CT were significant prognostic factors for PFS (all p<0.05). Among these parameters, only the IPI score was an independent predictor for PFS (p=0.044). Survival of patients with a high IPI score (≥3) was poorer than those with a low IPI score (0–2; p<0.001).ConclusionDespite a negative interim 18F-FDG PET/CT, approximately 39% of DLBCL patients showed progression during follow-up. Although the negative PET/CT was obtained during chemotherapy, it is important to closely follow-up patients, especially those with a high IPI score.