利用放射生物学模型比较周围型肺癌立体定向放射治疗中的3种剂量方案

Comparison among 3 dose schedules in stereotactic body radiotherapy for peripheral lung cancer based on radiobiological models

目的:利用放射生物学模型比较周围型肺癌立体定向放射治疗(SBRT)中3种常见剂量方案3×15 Gy、4×12 Gy和3×18 Gy在肿瘤局部控制率(TCP)、放射性肺炎(RIP)、胸壁疼痛(CWP)和肋骨骨折(RIRF)发生概率方面的差异。方法:收集20例周围型早期肺癌的CT图像资料,分别采用3种剂量方案设计放射治疗计划,利用放射生物学模型计算每种剂量方案的TCP、RIP、CWP和RIRF概率值。结果:3种剂量方案对TCP没有显著影响;4×12 Gy剂量方案的放疗毒性最低,3×15 Gy放疗毒性稍有增高,而3×18 Gy的毒性最高;3×18 Gy剂量方案的RIP、CWP和RIRF发生概率均明显高于其它两种剂量方案。结论:3种剂量方案的TCP数值没有显著差别,4×12 Gy剂量方案的放疗毒性最低,3×18 Gy剂量方案显著增加RIP、CWP和RIRF的发生概率,建议临床治疗前应根据肿瘤与危及器官的毗邻关系选择合适的剂量方案,实施个体化治疗策略。

Objective To investigate the effects of 3 common dose schedules,namely 3×15 Gy,4×12 Gy and 3×18 Gy,in stereotactic body radiotherapy for peripheral lung cancer on tumor control probability(TCP)and the probabilities of occurrence of radiationinduced pneumonitis(RIP),chest wall pain(CWP)and radiation-induced rib fracture(RIRF)using radiobiological models.Methods The CT images of 20 cases of peripheral lung cancer were collected.Three groups of treatment plans were designed based on 3 dose schedules.The TCP and the probabilities of occurrence of RIP,CWP and RIRF in each dose schedule were calculated by radiobiological models.Results Dose schedule had trivial effects on TCP.Radiation-induced toxicities in 3×18 Gy dose schedule was the highest,followed by 3×15 Gy dose schedule and 4×12 Gy dose schedule.Moreover,the probabilities of occurrence of RIP,CWP and RIRF in 3×18 Gy dose schedule were significantly higher than those in the other 2 dose schedules.Conclusion There is no significant difference in TCP among 3 different dose schedules.The radiation-induced toxicities in 4×12 Gy dose schedule is the lowest;and 3×18 Gy dose schedule results in higher probabilities of occurrence of RIP,CWP and RIRF.The adjacence between the tumor and organs-at-risk should be considered before clinical treatment for determining patient-specific dosing strategy and implementing individualized treatment.