Tomé Wolfgang A, Hodge C Wesley, Mehta Minesh P, Bentzen Søren M
Departments of Human Oncology and Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, USA.
Department of Radiation Oncology, Robert Boissoneault Oncology Institute, Ocala, Florida, USA.
J Radiosurg SBRT. 2011;1(2):155-161.
PURPOSE/OBJECTIVES: Late complications of SBRT include radiation related rib fractures. We estimate the incidence of rib fracturesas a function of maximum absorbed rib dose after stereotactic body radiotherapy (SBRT) for early stage lung cancer.
MATERIALS/METHODS: Of 23 patients treated with image guided SBRT (60 Gy in 5 fractions) between 2003 and 2006, 4 developed pathological rib fractures near the SBRT planning target volume (). Both planned maximum dose and maximum Fraction-size equivalent dose () to the combined rib volume lying within the prescription isodose volume was determined and a probit dose response model was fitted to the observed rib fracture data for each.
17 patients were evaluated, all with a minimum of 15 months follow-up. Median followup was 43 months (range 15-60 months). The median time to rib fracture was 26.5 months (range 15-34 months). The maximum rib dose ranged from 23.8-74.7 Gy (median 57.8 Gy) in 5 fractions. Dose was a significant predictor of rib fracture (p=0.02), with a D () estimate of 66.71 Gy (73.52 Gy). The steepness of the dose-response curve was quantified by the m and 50 value, estimated at = 0.1663 and = 2.39 for the maximum dose probit dose response model and at = 0.2747 and = 1.45 for the maximum probit dose response model.
Maximum rib dose should be carefully considered in SBRT with appropriate risk counseling of patients whose maximum rib dose exceeds a dose of 50 Gy in 5 fractions or a maximum of 43.1 Gy, estimated to be associated with a 6.6 % risk of rib fractures. Hence, the inclusion of ribs as an "organ at risk" in intensity modulated radiotherapy (IMRT) planning should be considered as a way to reduce the likelihood of rib fractures.
目的/目标：立体定向体部放疗（SBRT）的晚期并发症包括与放疗相关的肋骨骨折。我们评估了早期肺癌立体定向体部放疗（SBRT）后肋骨骨折的发生率与肋骨最大吸收剂量之间的关系。
材料/方法：2003年至2006年间接受影像引导SBRT（5次分割，每次60 Gy）治疗的23例患者中，有4例在SBRT计划靶区附近发生了病理性肋骨骨折。确定了位于处方等剂量体积内的联合肋骨体积的计划最大剂量和最大分次剂量当量（），并将概率剂量反应模型拟合到每个患者的观察到的肋骨骨折数据。
对17例患者进行了评估，所有患者至少随访15个月。中位随访时间为43个月（范围15 - 60个月）。肋骨骨折的中位时间为26.5个月（范围15 - 34个月）。5次分割中肋骨最大剂量范围为23.8 - 74.7 Gy（中位值57.8 Gy）。剂量是肋骨骨折的显著预测因素（p = 0.02），最大剂量概率剂量反应模型的D（）估计值为66.71 Gy（73.52 Gy）。剂量反应曲线的斜率通过m和50值进行量化，最大剂量概率剂量反应模型的估计值分别为 = 0.1663和 = 2.39，最大 概率剂量反应模型的估计值分别为 = 0.2747和 = 1.45。
在SBRT中，当患者的肋骨最大剂量超过5次分割50 Gy或最大 43.1 Gy时，应仔细考虑最大肋骨剂量，并对患者进行适当的风险咨询，据估计这与6.6%的肋骨骨折风险相关。因此，在调强放疗（IMRT）计划中应考虑将肋骨作为“危及器官”纳入，以降低肋骨骨折的可能性。
