Center for Proton Therapy, Paul Scherrer Institute, Villigen, Switzerland.
Int J Radiat Oncol Biol Phys. 2013 May 1;86(1):108-13. doi: 10.1016/j.ijrobp.2012.11.041. Epub 2013 Jan 16.
Irradiation of pediatric facial structures can cause severe impairment of permanent teeth later in life. We therefore focused on primary and permanent teeth as organs at risk, investigating the ability to identify individual teeth in children and infants and to correlate dose distributions with subsequent dental toxicity.
We retrospectively reviewed 14 pediatric patients who received a maximum dose >20 Gy(relative biological effectiveness, RBE) to 1 or more primary or permanent teeth between 2003 and 2009. The patients (aged 1-16 years) received spot-scanning proton therapy with 46 to 66 Gy(RBE) in 23 to 33 daily fractions for a variety of tumors, including rhabdomyosarcoma (n=10), sarcoma (n=2), teratoma (n=1), and carcinoma (n=1). Individual teeth were contoured on axial slices from planning computed tomography (CT) scans. Dose-volume histogram data were retrospectively obtained from total calculated delivered treatments. Dental follow-up information was obtained from external care providers.
All primary teeth and permanent incisors, canines, premolars, and first and second molars were identifiable on CT scans in all patients as early as 1 year of age. Dose-volume histogram analysis showed wide dose variability, with a median 37 Gy(RBE) per tooth dose range across all individuals, and a median 50 Gy(RBE) intraindividual dose range across all teeth. Dental follow-up revealed absence of significant toxicity in 7 of 10 patients but severe localized toxicity in teeth receiving >20 Gy(RBE) among 3 patients who were all treated at <4 years of age.
CT-based assessment of dose distribution to individual teeth is feasible, although delayed calcification may complicate tooth identification in the youngest patients. Patterns of dental dose exposure vary markedly within and among patients, corresponding to rapid dose falloff with protons. Severe localized dental toxicity was observed in a few patients receiving the largest doses of radiation at the youngest ages; however, multiple factors including concurrent chemotherapy confounded the dose-effect relationship. Further studies with larger cohorts and appropriate controls will be required.
儿童面部结构的辐射会导致其永久性牙齿在以后的生活中严重受损。因此，我们将重点放在原发性和永久性牙齿作为危险器官上，研究识别儿童和婴儿个体牙齿的能力，并将剂量分布与随后的牙齿毒性相关联。
我们回顾性分析了 2003 年至 2009 年间 14 名接受最大剂量> 20 Gy（相对生物学效应，RBE）的原发性或永久性牙齿的儿科患者。这些患者（年龄 1-16 岁）接受了点扫描质子治疗，46-66 Gy（RBE），共 23-33 天，用于治疗多种肿瘤，包括横纹肌肉瘤（n=10）、肉瘤（n=2）、畸胎瘤（n=1）和癌（n=1）。在计划 CT 扫描的轴位切片上勾勒出单个牙齿轮廓。从总计算的治疗中获得了剂量-体积直方图数据。从外部护理提供者获得了牙齿随访信息。
所有原发性牙齿和恒切牙、尖牙、前磨牙、第一和第二磨牙都可以在所有患者的 CT 扫描中在 1 岁时识别。剂量-体积直方图分析显示剂量变化很大，所有个体的中位数为 37 Gy（RBE）/牙齿剂量范围，所有牙齿的中位数为 50 Gy（RBE）/个体内剂量范围。牙齿随访发现，10 名患者中有 7 名无明显毒性，但 3 名年龄均<4 岁的患者中，有 3 名患者接受>20 Gy（RBE）治疗的牙齿有严重局部毒性。
基于 CT 的个体牙齿剂量分布评估是可行的，尽管最小的患者可能会延迟钙化，从而使牙齿识别复杂化。在患者内部和之间，牙齿的剂量暴露模式差异很大，与质子的快速剂量衰减相对应。少数接受最大剂量辐射的患者出现严重局部牙齿毒性；然而，包括同时进行化疗在内的多种因素使剂量效应关系复杂化。需要进一步的研究，包括更大的队列和适当的对照。
