PET-CT limitations in early stage non-small cell lung cancer: to whom more aggressive approach in radiotherapy and surgery should be directed?

This editorial comments on the study by Paravati et al., which reported on the incidence of occult regional lymph node metastases in PET-CT T1T2N0 non-small cell lung cancer (NSCLC) patients. A central location and the size of the tumor were shown to be the strongest predictors of the risk of occult nodal disease. Authors comment that in view of limitations of modern imaging, as well as the reported negative predictive value (NPV) of invasive staging methods, the choice of therapeutic options as the extent of surgery (lobectomy or sublobar resection) or radiotherapy [stereotactic body radiation therapy (SBRT) or conformal radiotherapy (RT) with some forms of elective nodal irradiation (ENI)] should consider tumor’s characteristics and not be based only on imaging and invasive staging modalities.     

肝癌立体定向体部放射治疗的剂量学研究

目的：探讨立体定向体部放射治疗（stereotactic body radiotherapy,SBRT）在原发性肝癌（Primary he-patic carcinoma,PHC）放疗中的剂量学特点和临床价值,证实SBRT是PHC放射治疗的发展方向。方法：2009年1月至8月,可行放疗的PHC患者50例,CT薄层定位扫描,将图像分别输入SBRT和三维适形放射治疗（3DCRT）计划系统,同一病例做两个治疗计划,对靶区内剂量分布、危及器官（OARs）受量、适形度等进行对比。结果：SBRT计划中靶区剂量显著高于3DCRT,正常肝脏和邻近OARs的重要剂量学指标均显著性低于3DCRT,两计划中适形指数（CI）和病灶覆盖率（Coverage）无统计学差异（P〉0.05）,均匀指数（HI）对比差异有显著性（P〈0.05）。SBRT治疗后3个月左右复查CT,观察疗效。50例患者均完成治疗和接受随访复查,局部控制率为88%,半年、1年生存率分别为86%、70%。不良反应少且轻,经处理可缓解消失。结论：SBRT在肝癌放疗中具有明显的剂量学优势,值得推广运用。     

中央型肺癌应用IMRT和3-DCRT实现SBRT的剂量学比较

目的:通过剂量学研究为立体定向放疗(SBRT)应用于中央型肺癌提供理论依据;通过比较中央型肺癌在三维适形放疗(3-DCRT)、动态调强放疗(DMLC-IMRT)技术下实现SBRT后肿瘤靶区和周围正常组织的剂量学差异,为SBRT应用于中央型肺癌提供剂量学依据。方法:对近1年内收治的30例中央型非小细胞肺癌患者设计处方剂量和治疗间隔相同的9野IMRT、3-DCRT和7野IMRT立体定向放疗(SBRT)计划,采用剂量体积直方图评价不同计划靶区和正常组织照射剂量以及适形指数(CI)和不均匀性指数(HI)。结果:SBRT应用于中央型肺癌的满足剂量学要求;三组计划比较,7野IMRT较其他两种计划对正常组织的保护性更好。结论:从剂量学角度分析SBRT可以应用于中央型肺癌;7野IMRT计划较其他两种计划在剂量学上更有优势。     

Clinical feasibility of using an EPID in CINE mode for image-guided verification of stereotactic body radiotherapy

PURPOSE: To introduce a novel method for monitoring tumor location during stereotactic body radiotherapy (SBRT) while the treatment beam is on by using a conventional electronic portal imaging device (EPID). METHODS AND MATERIALS: In our clinic, selected patients were treated under a phase I institutional review board-approved SBRT protocol for limited hepatic metastases from solid tumors. Before treatment planning multiple gold fiducial markers were implanted on the periphery of the tumor. During treatment the EPID was used in cine mode to collect the exit radiation and produce a sequence of images for each field. An in-house program was developed for calculating the location of the fiducials and their relative distance to the planned locations. RESULTS: Three case studies illustrate the utility of the technique. Patient A exhibited a systematic shift of 4 mm during one of the treatment beams. Patient B showed an inferior drift of the target of approximately 1 cm from the time of setup to the end of the fraction. Patient C had a poor setup on the first day of treatment that was quantified and accounted for on subsequent treatment days. CONCLUSIONS: Target localization throughout each treatment beam can be quickly assessed with the presented technique. Treatment monitoring with an EPID in cine mode is shown to be a clinically feasible and useful tool.