Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109, USA.
Int J Radiat Oncol Biol Phys. 2012 Oct 1;84(2):e245-9. doi: 10.1016/j.ijrobp.2012.03.031. Epub 2012 May 12.
To evaluate the variability of organ at risk (OAR) delineation and the resulting impact on intensity modulated radiation therapy (IMRT) treatment plan optimization in head-and-neck cancer.
An expert panel of 3 radiation oncologists jointly delineated OARs, including the parotid and submandibular glands (SM), pharyngeal constrictors (PC), larynx, and glottis (GL), in 10 patients with advanced oropharynx cancer in 3 contouring sessions, spaced at least 1 week apart. Contour variability and uncertainty, as well as their dosimetric impact on IMRT planning for each case, were assessed.
The mean difference in total volume for each OAR was 1 cm(3) (σ 0.5 cm(3)). Mean fractional overlap was 0.7 (σ 0.1) and was highest (0.8) for the larynx and bilateral SMs and parotids and lowest (0.5) for PC. There were considerable spatial differences in contours, with the ipsilateral parotid and PC displaying the most variability (0.9 cm), which was most prominent in cases in which tumors obliterated fat planes. Both SMs and GL had the smallest differences (0.5 cm). The mean difference in OAR dose was 0.9 Gy (range 0.6-1.1 Gy, σ 0.1 Gy), with the smallest difference for GL and largest for both SMs and the larynx.
Despite substantial difference in OAR contours, optimization was barely affected, with a 0.9-Gy mean difference between optimizations, suggesting relative insensitivity of dose distributions for IMRT of oropharynx cancer to the extent of OARs.
评估头颈部癌症中危及器官（OAR）勾画的可变性及其对调强放疗（IMRT）治疗计划优化的影响。
由 3 位放射肿瘤学家组成的专家小组在 3 次勾画会议中共同勾画了 10 例晚期口咽癌患者的 OAR，包括腮腺和颌下腺（SM）、咽缩肌（PC）、喉和声门（GL），每次间隔至少 1 周。评估了每个病例的轮廓变化和不确定性及其对 IMRT 计划的剂量学影响。
每个 OAR 的总体积的平均差异为 1 cm3（σ 0.5 cm3）。平均重叠分数为 0.7（σ 0.1），对于喉和双侧 SMs 和腮腺最高（0.8），对于 PC 最低（0.5）。轮廓存在明显的空间差异，同侧腮腺和 PC 显示出最大的变异性（0.9 cm），在肿瘤破坏脂肪平面的情况下最为明显。SMs 和 GL 的差异最小（0.5 cm）。OAR 剂量的平均差异为 0.9 Gy（范围 0.6-1.1 Gy，σ 0.1 Gy），GL 的差异最小，SMs 和喉的差异最大。
尽管 OAR 轮廓存在显著差异，但优化几乎没有受到影响，优化之间的平均差异为 0.9 Gy，表明对于口咽癌的 IMRT，剂量分布对 OAR 程度的相对不敏感。
