Tai P, Van Dyk J, Yu E, Battista J, Stitt L, Coad T
London Regional Cancer Centre and Department of Oncology, University of Western Ontario, Canada.
Int J Radiat Oncol Biol Phys. 1998 Sep 1;42(2):277-88. doi: 10.1016/s0360-3016(98)00216-8.
Three-dimensional (3D) conformal radiation therapy (CRT) assumes and requires the precise delineation of the target volume. To assess the consistency of target volume delineation by radiation oncologists, who treat esophageal cancers, we have performed a transCanada survey.
One of three case presentations, including CT scan images, of different stages of cervical esophageal cancer was randomly chosen and sent by mail. Respondents were asked to fill in questionnaires regarding treatment techniques and to outline boost target volumes for the primary tumor on CT scans, using ICRU-50 definitions.
Of 58 radiation oncologists who agreed to participate, 48 (83%) responded. The external beam techniques used were mostly anterior-posterior fields, followed by a multifield boost technique. Brachytherapy was employed by 21% of the oncologists, and concurrent chemotherapy by 88%. For a given case, and the three volumes defined by ICRU-50 (i.e., gross tumor volume [GTV], clinical target volume [CTV], and planning target volume [PTV]) we determined: 1. The total length in the cranio-caudal dimension; 2. the mean diameter in the transverse slice that was located in a CT slice that was common to all participants; 3. the total volume for each ICRU volume; and 4. the (5, 95) percentiles for each parameter. The PTV showed a mean length of 14.4 (9.6, 18.0) cm for Case A, 9.4 (5.0, 15.0) cm for Case B, 11.8 (6.0, 16.0) cm for Case C, a mean diameter of 6.4 (5.0, 9.4) cm for Case A, 4.4 (0.0, 7.3) cm for Case B, 5.2 (3.9, 7.3) cm for Case C, and a mean volume of 320 (167, 840) cm3 for Case A and 176 (60, 362) cm3 for Case C. The results indicate variability factors (95 percentile divided by 5 percentile values) in target diameters of 1.5 to 2.6, and in target lengths of 1.9 to 5.0.
There was a substantial inconsistency in defining the planning target volume, both transversely and longitudinally, among radiation oncologists. The potential benefits of 3D treatment planning with high-precision dose delivery could be offset by this inconsistency in target-volume delineation by radiation oncologists. This may be particularly important for multicenter clinical trials, for which quality assurance of this step will be essential to the interpretation of results.
三维（3D）适形放射治疗（CRT）假定并要求精确勾勒靶区体积。为评估治疗食管癌的放射肿瘤学家在靶区体积勾勒方面的一致性，我们开展了一项全加拿大范围的调查。
随机选取三份包含不同分期颈段食管癌CT扫描图像的病例资料之一，通过邮件发送。要求受访者填写关于治疗技术的问卷，并根据国际辐射单位与测量委员会（ICRU）-50的定义，在CT扫描图像上勾勒出原发肿瘤的加量靶区体积。
58位同意参与的放射肿瘤学家中，48位（83%）做出了回应。所采用的外照射技术大多是前后野，其次是多野加量技术。21%的肿瘤学家采用了近距离放疗，88%采用了同步化疗。对于给定病例以及ICRU-50定义的三个体积（即大体肿瘤体积[GTV]、临床靶区体积[CTV]和计划靶区体积[PTV]），我们确定了：1. 头脚方向的总长度；2. 在所有参与者共有的CT层面上的横断层面的平均直径；3. 每个ICRU体积的总体积；4. 每个参数的（5，95）百分位数。病例A的PTV平均长度为14.4（9.6，18.0）cm，病例B为9.4（5.0，1十五.0）cm，病例C为11.8（6.0，16.0）cm；病例A的平均直径为6.4（5.0，9.4）cm，病例B为4.4（0.0，7.3）cm，病例C为5.2（3.9，7.3）cm；病例A 的平均体积为320（167，840）cm³，病例C为176（60，362）cm³。结果表明，靶区直径的变异系数（95百分位数除以5百分位数）为1.5至2.6，靶区长度的变异系数为1.9至5.0。
放射肿瘤学家在横向和纵向定义计划靶区体积方面存在显著不一致。放射肿瘤学家在靶区体积勾勒上的这种不一致可能会抵消3D治疗计划与高精度剂量输送的潜在益处。这对于多中心临床试验可能尤为重要，因为这一步骤的质量保证对于结果的解释至关重要。
