Familial Nasopharyngeal Carcinoma 6

Advances in the Technology of Radiation 16Therapy for Nasopharyngeal CarcinomaLin Kong, Jiade J. Lu, and Nancy LeeCONTENTS16.1 Introduction 19716.2 Technical Advantages of IMRT 19816.3 Implementation of IMRT in NPC 19816.3.1 Patient Setup and Planning CT 19816.3.2 Definition and Dose Specifications ofTarget Volumes 19916.3.3 Delineation and Dose Limitations ofOrgans at Risk 20016.4 Treatment Planning and Delivery 20116.4.1 Treatment Planning 20116.4.2 IMRT Delivery 20316.5 Clinical Outcomes 20616.6 Treatment-Related Toxicity and Qualityof Life 20816.6.1 Acute Toxicity 20816.6.2 Late Toxicity 20816.6.3 Quality of Life 20916.7 Unresolved Issues 20916.8 Summary 210References 210Lin Kong, MDDepartment of Radiation Oncology, Fudan University ShanghaiCancer Center, 270 Dong An Road, Shanghai 200032,P.R. ChinaJiade J. Lu, MD, MBADepartment of Radiation Oncology, National University CancerInstitute, National University Health System,National Universityof Singapore, 5 Lower Kent Ridge Road, Singapore 119074,Republic of SingaporeNancy Lee, MDDepartment of Radiation Oncology, Memorial Sloan KetteringCancer Center, 1275 York Avenue, Box 22, New York, NY 10021,USA16.1IntroductionNasopharyngeal carcinoma (NPC) is highly sensitiveto ionizing radiation, and radiation therapy is themainstay treatment modality for nonmetastatic disease.For decades, NPC radiation therapy utilizes conventionaltreatment using two-dimentional and latelythree-dimentional techniques. Both techniques mainlyutilize opposed lateral fields with or without a supplementanterior field focused to the primary tumor todeliver tumoricidal doses of radiation. Disease controlusing conventional radiotherapy techniques has beenacceptable; however, insufficient dose to parts of thetargets owing to the proximity of the primary diseaseto critical structures such as optic chiasm, spinal cord,and/or brainstem may result in reduced disease controlin locally advanced NPC. Although the local controlof T1 and T2 NPC ranges between 76.6% and 93%,the reported overall local control rates were between58% and 79% in patients with locally advanced NPCtreated with conventional radiation (Ma et al. 2001;Leung et al. 2005; Au et al. 2003; Chua et al. 2001; Leeet al. 2005).Furthermore, high-dose irradiation using conventionalradiation has been associated with high probabilityof treatment-induced toxicities. While acuteside effects such as mucositis and skin reaction areusually self-limited and may subside spontaneouslywith supportive care, late-effects such as xerostomia,trismus, hearing loss, and more severely, temporallobe necrosis and spinal cord damage are usuallypermanent with devastating symptoms to patients.The introduction of intensity-modulated radiationtherapy (IMRT) has excited the profession of radiationoncology more than any other new technologysince the introduction of the linear accelerator. IMRTis of particular importance for the treatment of head