Quantitative evaluation and prediction of treatment response with volumetric FDG PET parameters in follicular lymphoma

Objectives Follicular lymphoma(FL) often represents low FDG uptake in PET before treatment(Tx), which potentially affects visual assessment of Tx response. In the present study, SUV-related or volumetric(VOL) FDG PET parameters were used to quantitatively evaluate and predict Tx response in FL. The results were compared to ones from revised response criteria(RRC) based on visual evaluation of FDG uptake.

Methods This study included 45 pre- and postTx FDG PET/CT exam sets in 42 FL patients. SUVmax and SUVpeak(1cm³ ROI) were obtained in the hottest lesion in each exam. Metabolic tumor volume(MTV) and total lesion glycolysis(TLG) were calculated as VOL parameters for the hottest as well as whole-body(wb) lesions(SUV threshold 2.5). Changes of these parameters after Tx were evaluated according to PET response criteria in solid tumors(PERCIST) and compared to RRC results. The parameters were also evaluated as to prediction of Tx response and recurrence within 2 years.

Results PreTx SUVmax ranged from 2.7 to 17.8(mean:6.8±3.5), with low FDG uptake(SUVmax ≤5) in 20(44%) of 45 exams. SUVmax exhibited a strong correlation with SUVpeak(r=0.99), but a weak correlation with MTV or TLG(r=0.32-0.41). PERCIST with VOL parameters provided concordant results with RCC(42-43 of 45 sets) more frequently than PERCIST with SUVmax or peak(39, 40 sets, respectively). PreTx parameters had no correlations with Tx response nor recurrence. PostTx parameters as well as changes of VOL parameters after Tx correlated to the recurrence(r=0.56-0.62), but ROC analysis revealed postTx SUVmax the best parameter to determine recurrence(AUC:0.83, sen.68%, spe.96%, acc.82%).

Conclusions This study demonstrated VOL FDG PET parameters were useful than SUVmax or peak in evaluating Tx response in FL, resolving discordant results between PERCIST with SUV-related parameters and RRC. SUV-related and VOL PET parameters were comparable in prediction of Tx response or recurrence in this study.