体质量监测对乳腺癌根治术后放疗摆位误差的影响研究

Influence of body mass monitoring on radiotherapy positioning error after radical mastectomy for breast cancer

目的:观察不同身体质量指数(body mass index,BMI)的乳腺癌根治术后患者的放疗摆位误差,探讨体质量监测对摆位误差的影响。方法:选取2018年6月至2019年9月在武汉大学人民医院接受乳腺癌根治术的38例患者,根据BMI值分为未超重组(BMI<24 kg/m2,20例)和超重组(BMI≥24 kg/m2,18例),通过锥形束CT(cone-beam CT,CBCT)影像验证获取患者左右(X)、头脚(Y)、前后(Z)3个方向的摆位误差,根据公式分别计算出2组患者临床靶区(clinical target volume,CTV)至计划靶区(planning target volume,PTV)各方向的外扩边界(MPTV)。通过统计2组患者放疗期间体质量的变化幅度值,观察体质量变化对摆位误差的影响。采用SPSS 22.0软件进行统计学分析。结果:未超重组和超重组患者在X轴平移方向的摆位误差分别为(1.75±1.38)与(2.26±2.12)mm,差异具有统计学意义(P<0.05),在其他方向上的平移及旋转误差值无统计学差异(P>0.05)。未超重组和超重组患者在X、Y、Z轴方向的外扩边界分别为5.02、6.09、3.88 mm与6.48、6.23、4.38 mm。未超重组体质量变化幅度在<2%与2%~4%区间的患者在Z轴平移方向的摆位误差值分别为(1.33±1.12)与(2.36±1.62)mm,差异具有统计学意义(P<0.05);超重组体质量变化幅度在<2%与2%~4%区间的患者在X轴平移方向的误差值分别为(2.49±2.30)与(1.28±1.24)mm,差异具有统计学意义(P<0.05)。结论:乳腺癌根治术后放疗中,BMI及体质量的变化与摆位误差存在相关性,对于不同BMI的患者进行放疗计划设计时,需根据个体差异给予合适的外扩边界。

Objective To observe the positioning errors of radiotherapy in patients with different body mass indexes(BMI)after radical mastectomy and investigate the influence of body mass monitoring on the position error.Methods Thirty-eight patients who underwent radical mastectomy at Wuhan University People's Hospital from June 2018 to September 2019 were selected and divided into a non-overweight group(BMI<24 kg/m2,20 cases)and an overweight group(BMI≥24 kg/m2,18 cases).The cone-beam CT(CBCT)image validation was used to obtain the positioning errors in the left-right(X),head-foot(Y)and anterior-posterior(Z)directions of the patients,and the MPTV of the clinical target volume(CTV)to the planning target volume(PTV)in each direction was calculated according to the equation for all the patients.The body mass changes during radiotherapy of the patients were counted and the effect of body mass change on the positioning error was observed.SPSS 22.0 software was used for statistical analysis.Results The positioning errors of the patients in the X-axis translation direction in the non-overweight group((1.75±1.38)mm)were significantly different with those in the overweight group((2.26±2.12)mm)(P<0.05),while the translation and rotation errors in the other directions had no statistical difference in the two groups(P>0.05).The non-overweight group had the values of MPTV in the X,Y and Z directions being 5.02,6.09,3.88 mm and the overweight group had the values being 6.48,6.23,4.38 mm,respectively.In the non-overweight group the patients with a<2%body mass variation had the positioning errors in the Z-axis translation direction((1.33±1.12)mm)significantly different with those of the patients with a 2%-4%variation((2.36±1.62)mm)(P<0.05);in the overweight group the patients with a<2%body mass variation had the positioning errors in the X-axis translation direction((2.49±2.30)mm)significantly different with those of the patients with a 2%-4%variation((1.28±1.24)mm)(P<0.05).Conclusion There is a correlation between the changes in BMI and body mass and positioning error in the radiotherapy after radical mastectomy.Appropriate MPTV has to be tailored when designing radiotherapy plans for patients with different BMIs.