Aoki Masahiko, Sato Mariko, Hirose Katsumi, Akimoto Hiroyoshi, Kawaguchi Hideo, Hatayama Yoshiomi, Ono Shuichi, Takai Yoshihiro
Department of Radiology and Radiation Oncology, Graduate School of Medicine, Hirosaki University, 5 Zaifu-cho, Hirosaki, Aomori, 036-8562, Japan.
Department of Radiation Oncology, Southern Tohoku Proton Therapy Center, 7-172 Yatsuyamada, Koriyama, Fukushima, 963-8052, Japan.
Radiat Oncol. 2015 Apr 22;10:99. doi: 10.1186/s13014-015-0406-8.
Radiation-induced rib fracture after stereotactic body radiotherapy (SBRT) for lung cancer has been recently reported. However, incidence of radiation-induced rib fracture after SBRT using moderate fraction sizes with a long-term follow-up time are not clarified. We examined incidence and risk factors of radiation-induced rib fracture after SBRT using moderate fraction sizes for the patients with peripherally located lung tumor.
During 2003-2008, 41 patients with 42 lung tumors were treated with SBRT to 54-56 Gy in 9-7 fractions. The endpoint in the study was radiation-induced rib fracture detected by CT scan after the treatment. All ribs where the irradiated doses were more than 80% of prescribed dose were selected and contoured to build the dose-volume histograms (DVHs). Comparisons of the several factors obtained from the DVHs and the probabilities of rib fracture calculated by Kaplan-Meier method were performed in the study.
Median follow-up time was 68 months. Among 75 contoured ribs, 23 rib fractures were observed in 34% of the patients during 16-48 months after SBRT, however, no patients complained of chest wall pain. The 4-year probabilities of rib fracture for maximum dose of ribs (Dmax) more than and less than 54 Gy were 47.7% and 12.9% (p = 0.0184), and for fraction size of 6, 7 and 8 Gy were 19.5%, 31.2% and 55.7% (p = 0.0458), respectively. Other factors, such as D2cc, mean dose of ribs, V10-55, age, sex, and planning target volume were not significantly different.
The doses and fractionations used in this study resulted in no clinically significant rib fractures for this population, but that higher Dmax and dose per fraction treatments resulted in an increase in asymptomatic grade 1 rib fractures.
近期有报道称，立体定向体部放疗（SBRT）治疗肺癌后出现放射性肋骨骨折。然而，采用中等分割剂量且长期随访的SBRT后放射性肋骨骨折的发生率尚不清楚。我们研究了采用中等分割剂量的SBRT治疗周围型肺肿瘤患者后放射性肋骨骨折的发生率及危险因素。
2003年至2008年期间，41例患有42个肺部肿瘤的患者接受了SBRT治疗，分9至7次给予54至56 Gy的剂量。研究的终点是治疗后通过CT扫描检测到的放射性肋骨骨折。选择所有照射剂量超过处方剂量80%的肋骨并进行轮廓勾画，以构建剂量体积直方图（DVH）。本研究对从DVH中获得的几个因素以及通过Kaplan-Meier方法计算的肋骨骨折概率进行了比较。
中位随访时间为68个月。在75根勾画轮廓的肋骨中，SBRT后16至48个月内，34%的患者出现了23处肋骨骨折，但无患者主诉胸壁疼痛。肋骨最大剂量（Dmax）大于和小于54 Gy时，4年肋骨骨折概率分别为47.7%和12.9%（p = 0.0184）；分割剂量为6、7和8 Gy时，4年肋骨骨折概率分别为19.5%、31.2%和55.7%（p = 0.0458）。其他因素，如D2cc、肋骨平均剂量、V10 - 55、年龄、性别和计划靶体积，差异均无统计学意义。
本研究中使用的剂量和分割方式在该人群中未导致具有临床意义的肋骨骨折，但较高的Dmax和每次分割剂量的治疗会导致无症状的1级肋骨骨折增加。
