The effect of different segmentation methods on primary tumour metabolic volume assessed in 18F-FDG-PET/CT in patients with cervical cancer, for radiotherapy planning

Abstract

Introduction Gynaecological cancers, including cervical cancer, often require a multidisciplinary approach that includes external beam radiotherapy, chemotherapy, and/or surgical treatment. Biological parameters of the tumour evaluated in 18F-FDG-PET/CT are used for target volume delineation in radiotherapy planning. The choice of segmentation method may affect the assessment of metabolic tumour volume (MTV) in 18F-FDG-PET/CT. Aim of the study To find the optimal segmentation method for the assessment of primary MTV in 18F-FDG-PET/CT in cervical cancer patients for radiotherapy planning. Material and methods Retrospective analysis was performed on a group of 30 patients with newly diagnosed, histologically confirmed cervical cancer. The primary MTVs were assessed by SUVmax and SUVmean values; three segmentation methods were used to assess the primary MTV: constant threshold of SUVmax of 2.5, threshold of SUVmax 35%, and threshold of SUV max 45%. The MTVs were compared with the tumour volumes obtained in magnetic resonance imaging (MRI), which was the “gold standard”, to select the best optimal segmentation method reflecting the tumour size. Wilcoxon-Mann-Whitney and t-test were used for statistical analysis. Results Depending on the segmentation method chosen, significant differences in the MTVs were obtained (p < 0.001). The highest volumes were obtained using the method based on constant SUVmax of 2.5, while the smallest in case of threshold of SUVmax of 45%. Regarding the volume determined by MRI, a 35% SUVmax threshold was chosen as the most reliable method. Conclusions The choice of appropriate segmentation method has a significant impact on the primary MTV assessment in 18F-FDG-PET/CT in patients with cervical cancer.