肿瘤精确放疗新进展——图像引导自适应放疗

摘要

图像引导自适应放疗(ART)是一种新型的肿瘤精确放疗技术,它是继三维适形放疗(3D-CRT)和三维调强放疗(IMRT)之后,随着图像引导放疗(IGRT)的普遍应用而发展起来的.ART可以较好地解决放疗分次间的靶区位置和形态变化问题,适用于各种部位的肿瘤.对于鼻咽癌患者和(或)体重明显下降的头颈部肿瘤患者,采用ART可使PTV的边界缩小,减少腮腺等危及器官所受剂量,降低放疗毒副反应.对于胸腹部肿瘤,ART可有效解决分次治疗间的靶区运动问题,在提高肿瘤照射剂量的同时有效降低同侧正常肺组织的受照剂量,使肺毒性降到最低.前列腺癌由于受膀胱和直肠充盈程度的影响,靶区的变形有时会比较大,采用ART可显著降低直肠副反应发生的概率,也可消除直肠扩张对治疗的影响.而对膀胱癌和宫颈癌患者进行分次治疗时,采用在线ART技术更新治疗计划,可明显减少肿瘤靶区周围危及器官的辐射剂量,保护直肠和大肠等危及器官,从而降低放射性直肠炎、放射性膀胱炎等放疗并发症的发生概率.%Image-guided adaptive radiation therapy (ART) is one of the newly techniques in the field of precise radiotherapy, which is developed with the universal application of image-guided radiotherapy (IGRT) following by the three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (MRT). ART can effectively correct for inter- and intra-fraction variation during radiation therapy and is applicable for the treatment of various anatomical parts of the tumor. For patients with nasopharyngeal carcinoma and (or) weight loss, ART can achieve significant clinical efficacy of which reduces the margin of the planning target volume (PTV), accordingly reducing radiation dose of organs at risk such as the parotid so as to minimize the radioactive toxic side effects. ART really reduces the impact of interfractional variations in patient set-up and anatomy changes for the thoracic and abdominal tumors. Compared with conventional radiotherapy, Image-guided ART for lung cancer can increase tumor radiation dose, in the meanwhile effectively reducing exposure doses of the ipsilateral normal lung tissue for the purpose of minimizing pulmonary toxicity. Due to the degree of distention of the bladder and rectum, the target deformation of prostate cancer may change a lot sometimes. ART is also used to decrease the target margin, thereby not only reducing the probability of rectal adverse effects, but also eliminating of rectal distension on treatment. Besides, online ART can modify the treatment plan to reduce radiation dose of organs at risk (OAR) while consequently protecting the rectum and colon and other OARs and lessening radiotherapy complications such as radiation proctitis and radiocystitis.