Definition of gross tumor volume with FDG-18F PET-CT in patients with head and neck cancer: comparison of different delineation methods

ABSTRACT

Objective: Besides the high sensitivity and specificity of positron emission tomography (PET) for head and neck tumors, there is still a lack of consensus about how to use this method inradiotherapy planning. The aim of this study is to compare different gross tumor volume (GTV) obtained with PET images in comparison to the size of the target volume generated with CT scanalone, for treated and untreated head and neck lesions. Methods: Sixty lesions in fifty patients with head and neck squamous cell carcinoma were included in the study. Delineation of the GTV was achieved using computed tomography (CT) images alone (GTV-CT) and PET-CT images with the visual assessment method (GTVPET-CT) and standard uptake value (SUV) thresholds of 40, 50, 60 and 75 percent (GTV40%, GTV50%, GTV60%, GTV75%, respectively). Correlations were measured by the Spearman test and the Friedman test was used to verify differences between GTVs. Results: For all lesions (treated and untreated), only the GTVPET-CT showed a strong correlation with GTV-CT. For only the untreated lesions, GTVPET-CT and GTV75% showed a strong correlation with GTV-CT. The GTV50%, GTV60% and GTV75% showed statistically significant difference in relation to GTV-CT, while GTVPET-CT and GTV40% were similar to GTV-CT. Conclusion: The use of PET-CT changes the volume of the final target in head and neck tumors,depending on the methodology used to calculate the GTV. The results presented here showed that the GTV40% and the GTVPET-CT are those who are closer to the target volumes delineated by conventional CT