ABSTRACT
We analyzed the data for 53 patients with histologically proven primary squamous cell carcinoma of the head and neck treated with radiotherapy between February 2006 and August 2009. All patients underwent contrast-enhanced (CE)-CT and (18)F-fluorodeoxyglucose (FDG)-PET before radiation therapy planning (RTP) to define the gross tumor volume (GTV). The PET-based GTV (PET-GTV) for RTP was defined using both CE-CT images and FDG-PET images. The CE-CT tumor volume corresponding to a FDG-PET image was regarded as the PET-GTV. The CE-CT-based GTV (CT-GTV) for RTP was defined using CE-CT images alone. Additionally, CT-GTV delineation and PET-GTV delineation were performed by four radiation oncologists independently in 19 cases. All four oncologists did both methods. Of these, PET-GTV delineation was successfully performed in all 19 cases, but CT-GTV delineation was not performed in 4 cases. In the other 15 cases, the mean CT-GTV was larger than the PET-GTV in 10 cases, and the standard deviation of the CT-GTV was larger than that of the PET-GTV in 10 cases. Sensitivity of PET-GTV for identifying the primary tumor was 96%, but that of CT-GTV was 81% (P < 0.01). In patients with oropharyngeal cancer and tongue cancer, the sensitivity of CT-GTV was 63% and 71%, respectively. When both the primary lesions and the lymph nodes were evaluated for RTP, PET-GTV differed from CT-GTV in 19 cases (36%). These results suggested that FDG-PET is effective for defining GTV in RTP for squamous cell carcinoma of the head and neck, and PET-GTV evaluated by both CE-CT and FDG-PET images is preferable to CT-GTV by CE-CT alone.
Subject(s)
Carcinoma, Squamous Cell/diagnostic imaging , Fluorodeoxyglucose F18 , Head and Neck Neoplasms/diagnostic imaging , Positron-Emission Tomography , Radiopharmaceuticals , Tomography, X-Ray Computed , Computer Simulation , Contrast Media/pharmacology , Female , Humans , Imaging, Three-Dimensional , Male , Observer Variation , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Positron emission tomography (PET), especially F-18 fluorodeoxyglucose (FDG)-PET, has been recently used to verify the target volume in radiation treatment planning (RTP) for malignancies. The utility of FDG-PET/CT in defining gross tumor volume (GTV) has been shown in many studies, and the target delineation by a fixed threshold of the maximum standardized uptake value (40-50%) is suggested to be useful in RTP for lung cancer, head and neck cancer, etc. But, the spatial resolution, sensitivity, and specificity of PET are not always enough to define the difference between the GTV and the clinical target volume(CTV). Furthermore, FDG-PET is frequently used in the clinical staging before the treatment, and is also applied to the response evaluation after the treatment. This review focuses on the developing applications of PET in radiation oncology.
