REVIEW www.nature.com/clinicalpractice/onc Technology Insight: PET and PET/CT in head and neck tumor staging and radiation therapy planning Steven J Frank, KS Clifford Chao*, David L Schwartz, Randal S Weber, Smith Apisarnthanarax and Homer A Macapinlac INTRODUCTION In the US, over 40,000 people are diagnosed with head and neck cancer each year. 1 Surgery and radiation therapy, either alone or in combination with chemotherapy, have been utilized for defini- tive locoregional treatment of head and neck cancers (i.e. nasopharyngeal, oropharyngeal, hypopharyngeal and laryngeal tumors). Recent phase III randomized data indicate that for patients with advanced-stage and high-risk features, postoperative chemoradiation improves locoregional control and overall survival. 2,3 Optimal treatment algorithms can only be used after an adequate staging workup has defined the local, regional, and distant extent of disease. During the past two decades cross-sectional imaging has revolutionized the practice of oncology by providing new ways to visualize internal human anatomy. Previously, internal human anatomy was defined with 2-dimensional imaging (i.e. conventional radiographs) relying upon bony landmarks, contrast enhancement, and extrapolation of cadaveric data. CT and MRI enhance our ability to detect sub-centimeter lesions and perineural spread with excellent resolution. 4 This improvement in visualization provides the anatomical information necessary to identify and delineate targets essential for the successful and precise administration of radiation therapy. In patients with head and neck cancer, involved lymph nodes are primarily identified by conventional imaging (CT or MRI) and biopsied to confirm metastatic disease. Takashima et al. 5 reported the sensitivity, specificity and accu- racy for extraorgan spread of primary tumors was 89%, 100% and 92% respectively for MRI, and 78%, 75% and 77% for CT. The anatomical information alone cannot definitively differen- tiate between tumors and benign tissue. It also cannot completely reveal histopathological and physiological characteristics or assessment of early response to therapy. 6 It should be noted that some enlarged nodes might only be reactive, while smaller nodes might harbor metastatic foci; therefore, tumors of similar sizes might The evolving utilization of functional imaging, mainly 2-[ 18 F]fluoro- 2-deoxyglucose ( 18 FDG) imaging, with positron emission tomography (PET) and PET/CT, is profoundly altering head and neck tumor staging approaches, radiation treatment planning, and follow-up management. Tumor–node–metastasis staging with PET/CT has improved the characterization of patient disease versus CT, MRI, or PET alone, thereby affecting patient disease management. Therefore, the utilization of PET/CT is appropriate for head and neck cancer staging in the initial presentation and in the recurrent setting. In the setting of radiation therapy treatment planning, PET-directed tumor volume contouring is not ready for clinical practice without further technological improvements in imaging specificity/sensitivity and resolution. Patient or organ motion might interfere with the accuracy of anatomical co-alignment, and variability in defining the threshold of imaging signals on PET images can affect the contour of the biological tumor volume. The use of PET/CT for staging and detecting both primary and recurrent head and neck cancer is valuable; however, its application in radiation treatment planning should be viewed as investigational. KEYWORDS FDG, head and neck cancer, PET/CT, radiation therapy, treatment planning SJ Frank is Assistant Professor of Radiation Oncology, KSC Chao is Associate Professor of Radiation Oncology and Director of Molecular Image-guided Therapy, DL Schwartz is Assistant Professor of Radiation Oncology, RS Weber is the Hubert L and Olive Stringer Distinguished Professor and Chairman of the Department of Head and Neck Surgery, S Apisarnthanarax is at the Department of Experimental Radiation Oncology, and HA Macapinlac is Associate Professor of Nuclear Medicine, all at the University of Texas MD Anderson Cancer Center, Houston, TX, USA. Correspondence *Division of Radiation Oncology, Box 97, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, USA cchao@mdanderson.org Received 9 May 2005 Accepted 19 August 2005 www.nature.com/clinicalpractice doi:10.1038/ncponc0322 REVIEW CRITERIA Data for this review were obtained using PubMed and MEDLINE databases. PubMed was searched using Entrez for articles published up to 30 April 2005, including electronic early-release publications, and MEDLINE was searched for articles published from 1966 to April 2005 using OVID. Only manuscripts written in English were reviewed. Full articles were obtained and references were checked for additional material when appropriate. Search terms used included “PET”, “PET-CT”, “head and neck cancer”, “radiation therapy treatment planning”, “staging in head and neck cancer”. SUMMARY 526 NATURE CLINICAL PRACTICE ONCOLOGY OCTOBER 2005 VOL 2 NO 10 Nature Publishing Group ©2005