早期乳腺癌保乳术后动态与静态调强放疗技术的剂量学对比分析

Dosimetric analysis and comparison of dynamic and static intensity-modulated radiation therapy after breast-conserving surgery in early breast cancer

目的比较早期乳腺癌保乳术后动态与静态调强放疗技术的剂量学差异。方法选取25例早期乳腺癌保乳术后患者,利用Eclipse 13.5计划系统分别为每位患者设计动态调强和静态调强治疗(6个不同子野强度水平),处方剂量均为50 Gy,常规分割照射(2 Gy/次),5次/周。比较不同计划靶区的剂量分布、危及器官的受量情况,并比较加速器的机器跳数和治疗执行时间,评估不同技术的执行效率。结果(1)动态调强适形度、均匀度均优于静态调强(均P<0.05),且随着子野强度水平升高静态调强靶区适形度、靶区剂量均匀性变好。(2)静态调强各组的机器跳数和计划执行时间均低于动态调强组(均P<0.05),而静态调强的机器跳数随着子野强度水平增加而增多、治疗时间随着子野强度水平增加而缩短,但差异均无统计学意义(均P>0.05)。(3)动态调强组患侧肺受照量、健侧肺、心脏、健侧乳的最大受照剂量均高于各静态调强组,但差异均无统计学意义(均P>0.05)。结论在对早期乳腺癌保乳术后患者的调强放疗过程中,动态调强计划与静态调强计划相比,能更好地满足靶区剂量要求,获得更好的靶区剂量分布,周围危及器官的受照量略高,但仍在可接受范围。

Objective To compare the dosimetric differences between dynamic and static intensity-modulated radiation therapy after breast-conserving surgery in early breast cancer.Methods Twenty-five patients with early breast cancer after breast-conserving surgery were selected.Each patient received dynamic and static intensity modulation therapy(six different subfield intensity levels)using Eclipse 13.5 planning system,with a prescription dose of 50 Gy,conventional fractionated irradiation of 2 Gy per time,5 times per week.Dose distribution and radiation doses of organs at risk were compared between different planning targets,monitor units and treatment execution time of accelerators were compared to evaluate the execution efficiency of different techniques.Results(1)Dynamic intensity modulation was superior to static intensity modulation in conformity index and heterogeneity index(all P<0.05),and conformity index and heterogeneity index of static intensity modulation targets were improved with the increase of subfield intensity level.(2)The static intensity modulation groups exhibited lower monitor units and treatment execution time than the dynamic intensity modulation group(all P<0.05),moreover,static intensity modulation presented increased monitor units and decreased treatment time when subfield intensity level rose,showing no statistically significant difference(all P>0.05).(3)The radiation dose of affected lung and the maximum radiation doses of contralateral lung,heart and breast side in the dynamic intensity modulation group were higher than those in the static intensity modulation groups,exhibiting no statistically significant difference(all P>0.05).Conclusion In the process of intensity-modulated radiation therapy for early breast cancer patients after breast-conserving surgery,dynamic intensity modulation plan can better meet target volume requirements and achieve superior target volume distribution,having slightly higher radiation dose of surrounding organs at risk which is within the range of acceptable level,as compared with static intensity modulation plan.