胸壁补偿膜厚度及患者体型特征对乳腺癌调强放疗摆位误差和剂量学的影响

Effects of chest wall compensation film thickness and patient's body characteristics on setup errors and dosimetry in intensity-modulated radiotherapy for breast cancer

目的:探讨胸壁补偿膜厚度及患者体型特征对乳腺癌患者手术后接受调强放疗治疗的摆位误差及放疗剂量的影响。方法:采用前瞻性研究方法,选取2021年1月至2023年6月阜阳市肿瘤医院肿瘤放疗中心治疗的103例乳腺癌患者,对患者进行锥形束CT检查,分析患者的体质量指数(BMI)、肿瘤位置、胸围、患侧乳腺体积对其摆位误差的影响,分析不同厚度的补偿膜对患者靶区、肺部、心脏、脊髓的放射剂量的影响。结果:不同BMI、不同患侧分布的乳腺癌患者在左右方向上的摆位误差无统计学意义(P>0.05);胸围≥89.0 cm、患侧乳腺体积≥650 cm^(3)患者的左右方向摆位误差大于胸围<89.0 cm、患侧乳腺体积<650 cm^(3)患者(P<0.05)。不同患侧分布的乳腺癌患者在上下方向上的摆位误差无统计学意义(P>0.05);BMI≥23.1 kg/m^(2)、胸围≥89.0 cm、患侧乳腺体积≥650 cm^(3)患者的上下方向摆位误差大于BMI<23.1 kg/m^(2)、胸围<89.0 cm、患侧乳腺体积<650 cm^(3)患者(P<0.05);不同BMI水平、不同胸围、不同乳腺体积、不同患侧分布的乳腺癌患者在前后方向上的摆位误差无统计学意义(P>0.05)。左侧乳腺癌病灶患者采用0.5 cm补偿膜和1.0 cm补偿膜的放射治疗计划靶区(PTV)D_(95%)、PTV靶区D_(5%)、左侧肺部V_(20%)、心脏V_(30%)、心脏平均剂量(D_(mean))、脊髓最大剂量(D_(max))、机器跳数(MU)、均匀性指数(HI)测定值比较,差异无统计学意义(P>0.05);采用0.5 cm补偿膜患者的适形度指数(CI)值低于采用1.0 cm补偿膜的乳腺癌患者(P<0.05),右侧乳腺癌病灶患者采用0.5 cm补偿膜和1.0 cm补偿膜的PTV靶区D_(95%)、PTV靶区D_(5%)、右侧肺部V_(20%)、脊髓D_(max)、MU、CI、HI测定值比较,差异无统计学意义(P>0.05)。结论:对于乳腺癌调强放疗患者,BMI、胸围、患侧乳腺体积均与摆位误差有关,采用0.5 cm和采用1.0 cm胸壁补偿膜均可以用于术后放疗,对放疗剂量和加速器跳数影响不大。

Objective To investigate the effects of the thickness of the chest wall compensation film and the patient's body characteristics on the setup errors and radiation dose of breast cancer patients receiving intensity-modulated radiotherapy following surgery.Methods A total of 103 patients with breast cancer who were treated in the Tumor Radiotherapy Center of Fuyang Cancer Hospital from January 2021 to June 2023 were selected for a prospective study.All patients received conebeam CT scan.The effects of body mass index(BMI),tumor location,chest circumference,and the affected breast volume on the setup errors were analyzed;and the effects of different compensation film thicknesses on the radiation doses to the planning target volume(PTV),lung,heart,and spinal cord were explored.Results The left-right setup errors didn't differ significantly in breast cancer patients with different BMI and affected sides(P>0.05);but the patients with chest circumference≥89.0 cm and affected breast volume≥650 cm^(3) had greater left-right setup errors than the other patients(chest circumference<89.0 cm and affected breast volume<650 cm^(3))(P<0.05).The difference in the superior-inferior setup errors was trivial in breast cancer patients with different affected sides(P>0.05),but the superior-inferior setup errors were greater in patients with BMI≥23.1 kg/m^(2),chest circumference≥89.0 cm,and breast volume on the affected side≥650 cm^(3) than the others(BMI<23.1 kg/m^(2),chest circumference<89.0 cm,and breast volume on the affected side<650 cm^(3))(P<0.05).There was no significant difference in the anterior-posterior setup errors in breast cancer patients with different BMI,chest circumferences,breast volumes,and affected sides(P>0.05).For left-sided breast cancer,the measured values of D_(95%)and D_(5%)of PTV,V_(20%)of left lung,V_(30%)and D_(mean) of heart,D_(max)of spinal cord,MU,and HI in patients with 0.5 and 1.0 cm compensation films were close(P>0.05);while lower CI was found in patients with 0.5 cm compensation film than those with 1.0 cm compensation film(P<0.05).For right-sided breast cancer,the measured values of D_(95%)and D_(5%)of PTV,V_(20%)of right lung,D_(max) of spinal cord,MU,CI,and HI didn't differ significantly between patients using 0.5 and 1.0 cm compensation films(P>0.05).Conclusion The BMI,chest circumference,and breast volume on the affected side in breast cancer patients undergoing intensity-modulated radiotherapy are all associated with the setup errors.Both 0.5 and 1.0 cm chest wall compensation films can be used for postoperative radiotherapy,which has little effect on the dosimetry and accelerator MU.