Clinical investigation
Head and neck
Impact of FDG-PET/CT Imaging on Nodal Staging for Head-And-Neck Squamous Cell Carcinoma

Presented at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), November 5–9, 2006, Philadelphia, PA.
https://doi.org/10.1016/j.ijrobp.2006.12.032Get rights and content

Purpose: To evaluate the impact of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) imaging on nodal staging for head-and-neck squamous cell carcinoma (SCC).

Methods and Materials: The study population consisted of 23 patients with head-and-neck SCC who were evaluated with FDG-PET/CT and went on to neck dissection. Two observers consensually determined the lesion size and maximum standardized uptake value (SUVmax) and compared the results with pathologic findings on nodal-level involvement. Two different observers (A and B) independently performed three protocols for clinical nodal staging. Methods 1, 2, and 3 were based on conventional modalities, additional visual information from FDG-PET/CT images, and FDG-PET/CT imaging alone with SUV data, respectively.

Results: All primary tumors were visualized with FDG-PET/CT. Pathologically, 19 positive and 93 negative nodal levels were identified. The SUVmax overlapped in negative and positive nodes <15 mm in diameter. According to receiver operating characteristics analysis, the size-based SUVmax cutoff values were 1.9, 2.5, and 3.0 for lymph nodes <10 mm, 10–15 mm, and >15 mm, respectively. These cutoff values yielded 79% sensitivity and 99% specificity for nodal-level staging. For Observer A, the sensitivity and specificity in Methods 1, 2, and 3 were 68% and 94%, 68% and 99%, and 84% and 99%, respectively, and Method 3 yielded significantly higher accuracy than Method 1 (p = 0.0269). For Observer B, Method 3 yielded the highest sensitivity (84%) and specificity (99%); however, the difference among the three protocols was not statistically significant.

Conclusion: Imaging with FDG-PET/CT with size-based SUVmax cutoff values is an important modality for radiation therapy planning.

Introduction

Advances in sophisticated radiotherapy (RT) techniques, notably three-dimensional conformal RT (3D-CRT) and intensity-modulated RT (IMRT), render the precise delineation of the gross tumor volume (GTV) essential for RT planning. This is particularly important in head-and-neck squamous cell carcinoma (SCC) where normal and abnormal structures are in close proximity. In the interpretation of morphologic imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI), the GTV boundary is often vague in the presence of inflammatory changes around the tumor or interference by metal artifacts, and their normal appearance on these images renders the detection of metastatic lymph nodes difficult. These factors contribute to a marked variability in GTV assessments even among experienced radiation oncologists, resulting in a possible geographic miss of the tumor or unnecessary irradiation of normal tissues (1).

Functional imaging with 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET), which provides information about glucose metabolism, may improve the consistency of GTV delineation (2, 3, 4). 18F-fluorodeoxyglucose PET and its quantitative parameter, the standardized uptake value (SUV), have been used to evaluate the staging, treatment response, and recurrence detection of a wide range of solid cancers, including head-and-neck SCC. The sensitivity and specificity of FDG-PET for the detection of nodal involvement reportedly were 61–96% and 80–99%, respectively; with CT/MRI they were 53–82% and 71–97% (4, 5, 6, 7). On the other hand, because of the limited anatomic resolution of FDG-PET, precise tumor localization requires careful correlation with structural images. Imaging with PET/CT provides the morphologic information of CT and the functional information of PET (8, 9, 10, 11, 12).

Although FDG-PET/CT imaging has been used in the evaluation of head-and-neck SCC, its role in initial staging has not been fully addressed (13, 14, 15). Some studies reported that RT planning was changed on the basis of information yielded on FDG-PET/CT fused images; however, they did not provide pathologic confirmation of the imaging findings (16, 17, 18). The purpose of this study was to evaluate the impact of FDG-PET/CT imaging on nodal staging for head-and-neck SCC.

Section snippets

Methods and Materials

Written prior informed consent to undergo FDG-PET/CT imaging and receive treatments was obtained from all patients. The institutional review board of our hospital approved this retrospective study; patient informed consent for inclusion in this study was waived. To protect patient privacy, we removed all identifiers from our records at the completion of our analyses.

Results

Dissection was performed at 35 neck sites; of the 23 patients, 11 underwent unilateral and 12 bilateral dissections; 28 positive and 529 negative lymph nodes were pathologically isolated from 112 nodal levels, of which 19 were positive and 93 negative. Pathologically, 1 patient had T1, 6 had T2, 9 had T3, and 7 had T4 tumors; nodal involvement was N0 in 8, N1 in 8, N2b in 6, and N2c in 1 patient.

In all 23 primary tumors, FDG-PET/CT fused images demonstrated FDG accumulation. Based on FDG-PET/CT

Discussion

18F-fluorodeoxyglucose PET, a functional imaging methodology that provides information about tissue glucose metabolism, has been used for the evaluation of head-and-neck SCC. In our study, FDG-PET/CT fused images demonstrated FDG accumulation in all of the 23 primary tumors we examined. Among three protocols for nodal staging, FDG-PET/CT imaging with SUV data (Method 3) yielded the most correct lymph node staging for each observer. Previous studies of nodal staging with FDG-PET alone reported

Acknowledgments

The authors thank Prof. Masanori Shinohara from the Department of Oral and Maxillofacial Surgery and Prof. Eiji Yumoto from the Department of Otolaryngology–Head and Neck Surgery at Kumamoto University Hospital for clinical data collection; and Mr. Shinya Yamamoto from Uozumi Clinic for technical assistance.

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