Objective: To explore the prognostic value of interim 18F-FDG PET/CT (i-PET/CT) scan for the patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL).
Methods: A total of 70 cases of initially diagnosed of DLBCL by 158 18F-FDG PET/CT scans in our hospital were retrospectively analyzed. The 5-point scale, the Lugano classification and maximum standardized uptake value induction (ΔSUVmax) criteria were used respectively to assess i-PET/CT scans. Receiver-operating characteristics (ROC) analysis was used to determine an optimal cutoff for ΔSUVmax. Progression-free survival (PFS) and overall survival (OS) times were estimated as prognostic indicators using the Kaplan-Meier method and Cox regression.
Results: Optimal cutoff to predict progression or death was 62% for ΔSUVmax. The positive predictive value (PPV) for 2-year PFS and OS of i-PET/CT diagnosed by 5-point scale was low, and could be improved by using the Lugano classification with decreased sensitivity or ΔSUVmax criteria. Kaplan-Meier survival curve analysis showed that the Lugano classification and ΔSUVmax were good predictors for PFS and OS, respectively, while the 5-point scale could only predict OS. Cox regression univariate analysis showed that the International Prognostic Index (IPI) score was better to predict PFS than 5-point scale, but worse than the three assessments in predicting OS. COX regression multivariate analysis showed that ΔSUVmax<62% was an independent risk factor of prognosis, while the Lugano classification was only the OS independent prognostic predictor.
Conclusion: Assessing i-PET/CT by 5-point scale is a limited value for predicting PFS and OS in DLBCL patients. The Lugano classification is recommended to discriminate the patients with poorer outcomes. The ΔSUVmax criteria for i-PET/CT of DLBCL patients is an independent prognostic predictor for PFS and OS, better than the IPI score.