Baseline metabolic tumor volume calculation using different SUV thresholding methods in Hodgkin lymphoma patients: Interobserver agreement and reproducibility across software platforms

Aim: Although it is not yet used in clinical practice, metabolic tumor volume (MTV) assessed on the baseline FDG-PET has shown consistent prognostic value in various lymphoma types. The aim of our study was to compare interobserver agreement and reproducibility across platforms of MTV calculation using different SUV thresholding methods in a large series of patients with newly diagnosed Hodgkin lymphoma. Materials and methods: We retrospectively studied 121 patients. MTV at baseline FDG-PET was independently computed by three readers with three programs of semi-automatic segmentation, Fiji, LifeX, and Accurate. MTV measurement was performed with different thresholds: SUV >2.5, SUV >4, and SUV >41% of SUV max. Results: At inter-observer agreement analysis all Intraclass Correlation Coefficients (ICCs) were excellent (ICC >0.9), except for Accurate SUV >41% of SUV max (ICC = 0.8). The highest correlations were obtained at the SUV >4 threshold. The second best was SUV >2.5 threshold. Regarding reproducibility across software, we found statistically significant differences between Fiji versus LifeX and Accurate at fixed thresholds and between LifeX and Accurate at SUV >41% of SUV max, while no significant differences emerged between LifeX and Accurate using fixed thresholds. Conclusion: The three SUV thresholds studied are all suitable for MTV calculation in terms of reproducibility. The best reproducibility is achieved using fixed thresholds, both SUV >4 and SUV >2.5. If more than one software has to be used in a study, we suggest the use of fixed thresholds and the platforms LifeX and Accurate.