Evaluation of therapeutic effect and prognostic value of ¹⁸F-FDG PET/CT in different treatment nodes of DLBCL patients

Background In the present study, we aimed to investigate the role of baseline (B), interim (I) and end-of-treatment (Eot) F-18-FDG PET/CT in assessing the prognosis of diffuse large B cell lymphoma (DLBCL), so as to identify patients who need intensive treatment at an early stage. Methods A total of 127 DLBCL patients (62 men; 65 women; median age 62 years) were retrospectively analyzed in this study. Baseline (n = 127), interim (n = 127, after 3-4 cycles) and end-of-treatment (n = 53, after 6-8 cycles) PET/CT images were re-evaluated; semi-quantitative parameters such as maximum standardized uptake value of lesion-to-liver ratio (SUVmax((LLR))) and lesion-to-mediastinum ratio (SUVmax((LMR))), total metabolic tumor volume (TMTV) and total metabolic tumor volume (TLG) were recorded. Delta TLG(1) was the change of interim relative to baseline TLG (I to B), Delta TLG(2) (Eot to B). Delta SUVmax and Delta TMTV were the same algorithm. The visual Deauville 5-point scale (D-5PS) has been adopted as the major criterion for PET evaluation. Visual analysis (VA) and semi-quantitative parameters were assessed for the ability to predict progression-free survival (PFS) and overall survival (OS) by using Kaplan-Meier method, cox regression and logistic regression analysis. When visual and semi-quantitative analysis are combined, the result is only positive if both are positive. Results At a median follow-up of 34 months, the median PFS and OS were 20 and 32 months. The survival curve analysis showed that advanced stage and IPI score with poor prognosis, Delta SUVmax((LLR))(1) < 89.2%, Delta TMTV1 < 91.8% and Delta TLG(1) < 98.8%, Delta SUVmax((LLR))(2) < 86.4% were significantly related to the shortening of PFS in patient (p < 0.05). Delta SUVmax((LLR))(1) < 83.2% and Delta TLG(1) < 97.6% were significantly correlated with the shortening of OS in patients (p < 0.05). Visual analysis showed that incomplete metabolic remission at I-PET and Eot-PET increased the risk of progress and death. In terms of predicting recurrence by I-PET, the combination of visual and semi-quantitative parameters showed higher positive predictive value (PPV) and specificity than a single index. Conclusion Three to four cycles of R-CHOP treatment may be a time point for early prediction of early recurrence/refractory (R/R) patients and active preemptive treatment. Combined visual analysis with semi-quantitative parameters of F-18-FDG PET/CT at interim can improve prognostic accuracy and may allow for more precise screening of patients requiring early intensive therapy.