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J Cancer 2017; 8(19):4117-4123. doi:10.7150/jca.21582 This issue Cite

Research Paper

Advantage of PET/CT in Target Delineation of MRI-negative Cervical Lymph Nodes In Intensity-Modulated Radiation Therapy Planning for Nasopharyngeal Carcinoma

Guanzhu Shen^1*, Weiwei Xiao^2*, Fei Han², Wei Fan³, Xiao-ping Lin³, Lixia Lu², Lie Zheng⁴, Ning Yue⁵, Bruce Haffty⁵, Chong Zhao^2✉, Xiaowu Deng^2✉

1. Department of Radiation Oncology, Affiliated Cancer Hospital & Institute of Guangzhou Medical University,78 Hengzhigang Road, Guangzhou 510095, China;
2. Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, 510060, P.R. China;
3. Department of Nuclear Medicine, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, 510060, P.R. China;
4. Department of Imaging, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, 510060, P.R. China.
5. Rutgers Cancer Institute of New Jersey, 195 Little Albany Street, New Brunswick, NJ, USA.
* Guanzhu Shen and Weiwei Xiao contributed equally to this work.

✉ Corresponding authors: Chong Zhao, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, 651 Dong Feng Road East, Guangzhou 510060, China Tel: +86-20-87342638 Fax: +86-20-87342638 Email: zhaochongorg.cn And Xiaowu Deng, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, 651 Dong Feng Road East, Guangzhou 510060, China Tel: +86-20-87343044 Fax: +86-20-87343044 Email: dengxwsysu.edu.cn More

Abstract

Introduction: In intensity-modulated radiation therapy (IMRT) planning for nasopharyngeal carcinoma (NPC), cervical lymph nodes (CLNs) that appear negative on magnetic resonance imaging (MRI) scans can be difficult to target. The purpose of this study was to assess the advantage of ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) for distinguishing MRI-negative CLNs and the effect of ¹⁸F-FDG PET/CT on diagnosis, target delineation, and dose prescription in IMRT planning for NPC.

Methods: Thirty-five NPC patients with 37 MRI-negative CLNs underwent ¹⁸F-FDG PET/CT imaging before treatment. Ultrasonography-guided fine-needle aspiration cytology (USgFNAC) was performed to examine the pathology of CLNs. The ¹⁸F-FDG PET/CT and cytopathological results were compared, and the diagnostic accuracy of ¹⁸F-FDG PET/CT was calculated. The cytopathologically confirmed CLNs were delineated and treated as the gross tumor volume of lymph nodes (denoted as GTVnd).

Results: Nineteen of the 37 MRI-negative CLNs were positive on ¹⁸F-FDG PET/CT, and metastasis was confirmed by USgFNAC in 16 CLNs. Of the remaining 18 ¹⁸F-FDG PET/CT-negative lymph nodes, metastasis was confirmed in one. The diagnostic accuracy, sensitivity, and specificity of ¹⁸F-FDG PET/CT were 89.2%, 94.1%, and 85.0%, respectively. The positive and negative predictive values were 84.2% and 94.4%, respectively. With a median follow-up of 48.3 months, no relapse was observed among the ¹⁸F-FDG PET/CT-positive CLNs with metastasis confirmed by USgFNAC and treated as GTVnd.

Conclusion: ¹⁸F-FDG PET/CT had high accuracy, sensitivity, and specificity for distinguishing MRI-negative CLNs. ¹⁸F-FDG PET/CT-positive CLNs could reasonably be categorized as high-risk clinical tumor volume in IMRT planning for NPC.

Keywords: ¹⁸F-FDG PET/CT, MRI, nasopharyngeal carcinoma, IMRT, cervical lymph nodes.

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