摘要
放射治疗是鼻咽癌的首选治疗手段。调强适形放疗(IMRT)既满足了鼻咽癌临床生物学行为对靶区的要求,同时满足了对头颈部重要器官功能保护的要求,在鼻咽癌的治疗中有着其它治疗无可比拟的优势,已成为鼻咽癌放疗的主流技术。靶区确定和勾画是IMRT的重点:大体肿瘤靶区包括鼻咽原发肿瘤及转移淋巴结;临床靶区根据受累的危险程度的不同分为高危区和低危区,不同的靶区给予不同的照射剂量。同常规放疗技术相比,IMRT提高了肿瘤区剂量,并使肿瘤区的剂量分布更加均匀,同时降低了正常组织受量,尤其在保护腮腺功能方面取得了理想的效果,有效缓解了鼻咽癌放疗后因唾液分泌不足造成的口干症状。而对于保护腮腺功能的限制剂量目前尚无定论。总结其临床应用结果,IMRT提高了肿瘤局控率,远处转移成为治疗失败主要原因,需采取综合治疗提高疗效。在采取何种方法降低肿瘤复发率的问题上仍存在争议。因鼻咽癌IMRT开展较晚,长期疗效有待进一步观察。IMRT目前存在的问题包括低剂量放射超敏感性造成的正常组织生物效应增加;分次照射时间延长导致的肿瘤区相对剂量率降低;不同单位在靶体积划分和勾画方面的差异等。在运用多种影像融合技术提高靶区勾画精确性以及利用乏氧细胞示踪技术实现生物适形等方面仍需近一步研究。
Radiotherapy is the best method to treat nasopharyngeal carcinoma. Intensity modulated radiotherapy （IMRT） has shown successful tumor targeting while simultaneously protecting critical normal tissues in the head and neck. It is better than other methods in treating nasopharyngeal carcinoma and is currently the most popular technique in this field. The definition of the target is critical. The gross tumor volume （GTV） involves the primary focus of the nasopharynx and positive neck nodes. The clinical target volume （CTV） is defined as a volume of high risk and a volume of low risk, based on the potential for tumor invasion. Different doses are intentionally delivered to different targets. Compared with conventional radiotherapy, IMRT can provide excellent tumor target coverage and allow the delivery of a high dose to the tumor while sparing nearby critical normal tissues. IMRT obtains especially good results near the parotid gland, resulting in significant improvement of xerostomia due to the low saliva flow after radiotherapy. There is no standard for dose limitation to effectively protect parotid function. Based on the results of the clinical treatment, excellent local-regional control for NPC was achieved with IMRT. Distant metastases represent the predominant mode of treatment failure. Combined modality therapy is required to improve outcomes. Controversies regarding the best method for reducing the recurrence rate remain. Further observation is needed to establish the long-term effects of this new modality. At present increased biological effects in normal tissue structures due to low dose hypersensitivity and relative low dose rates in tumor targets due to prolonged fraction delivery times remain a concern. Future direction will involve increasing the precision of tumor targeting using image fusion techniques and accomplishing biological conformality using a hypoxia tracer.
出处
《中国肿瘤临床》
CAS
CSCD
北大核心
2009年第9期533-537,共5页
Chinese Journal of Clinical Oncology
关键词
鼻咽肿瘤
调强适形放疗
腮腺功能
Nasopharyngeal neoplasm
Intensity modulated radiation therapy
Parotid function
