患者因素对乳腺癌保乳术后IMRT计划设计影响分析

目的 探讨患者VPTV、MHD、CLD、CTR对乳腺癌保乳术后IMRT计划设计的影响。方法 2016—2017年在我院接受全乳IMRT的48例女性乳腺癌保乳术后患者(左侧31例、右侧17例),放疗处方剂量为PTV 50 Gy,2 Gy/次。每个患者的调强计划同时使用物理参数和EUD对目标函数进行优化。采用一元和多元线性回归分析预测影响因子与OAR百分剂量体积、CI和HI间关系。结果 CTR和VPTV是左侧乳腺癌CI独立影响因素(R²值分别为0.56、0.56,P值分别为0.04、0)。CLD是左侧乳腺癌HI独立影响因素(R²=0.17,P=0.023),VPTV是右侧CI的独立影响因素(R²=0.48,P=0)。MHD和CTR是心脏VHeart30的预测因子。MHD和CLD是心脏DmaxHeart的预测因子。左侧乳腺癌预测公式为CI=0.38+0.32CTR,HI=1.06+0.02CLD。右侧CI=0.48。左侧Vlung20=12.68+3.18CLD,Vlung10=18.78+4.3CLD,Vlung5=26.2+5.2CLD,Dmeanlung=686.7+210.1CLD。心脏VHeart30=(-13.65)+30.5CTR+1.9MHD,DmaxHeart=5140.1+248.9MHD-195.6CLD。患者的心脏体积与MHD、VHeart10 、VHeart5、DmeanHeart和DmaxHeart无相关性。患者的全肺体积与CLD、Vlung20、Vlung10、Vlung5、Dmeanlung无相关性。左侧乳腺癌计划CI和HI的平均值分别为0.63±0.06(0.46~0.72)和1.09±0.02(1.074~1.14),右侧乳腺癌计划CI和HI的均值分别为0.65±0.08(0.48~0.76)和1.09±0.04(1.03~1.18)。结论 CTR、CLD和MHD可以预测左侧乳腺癌调强计划各个参数的合理性,右侧乳腺癌则不适用。据此生成的计算公式可以帮助物理师选择优选的射野设置方式,提高治疗计划的质量。

Impacts of patient factors on intensity-modulated radiotherapy planning after breast-conserving surgery for breast cancer

Objective To investigate the impacts of planning target volume (VPTV), maximal heart distance (MHD), central lung distance (CLD), and cardiothoracic ratio (CTR) on intensity-modulated radiotherapy (IMRT) after breast-conserving surgery for breast cancer. Methods Forty-eight patients with breast cancer (31 with left-sided breast cancer and 17 with right-sided breast cancer) who received whole-breast IMRT after breast-conserving surgery in our hospital from 2016 to 2017 were enrolled as subjects. The prescribed radiation dose for PTV was 50 Gy in 25 fractions. In IMRT planning for each patient, the Objective function was optimized using physical parameters and the equivalent uniform dose. The relationship of influencing factors with dose-volume histogram, conformal index (CI), and homogeneity index (HI) for organ at risk was predicted using univariate and multivariate linear regression analyses. Results CTR and VPTV were independent influencing factors for CI in patients with left-sided breast cancer (R²=0.56, P=0.04;R²=0.56, P=0.00). CLD was an independent influencing factor for HI in patients with left-sided breast cancer (R²=0.17, P=0.023). VPTV was an independent influencing factor for CI in patients with right-sided breast cancer (R²=0.48, P=0.00). MHD and CTR were predictors for VHeart30 of the heart. MHD and CLD were predictors for DmaxHeart of the heart. The prediction formulae for left-sided breast cancer were CI=0.38+0.32CTR and HI=1.06+0.02CLD. CI was 0.48 at the right side. At the left side, Vlung20=12.68+3.18CLD, Vlung10=18.78+4.3CLD, Vlung5=26.2+5.2CLD, and Dmeanlung=686.7+210.1CLD. For the heart, VHeart30=-13.65+30.5CTR+1.9MHD and DmaxHeart=5140.1+248.9MHD-195.6CLD. There was no correlation of patient′s heart volume with MHD, VHeart10, VHeart5, DmeanHeart, or DmaxHeart. There was no correlation of whole lung volume with CLD, Vlung20, Vlung10, Vlung5, or Dmeanlung. The mean values of CI and HI were 0.63±0.06(0.46-0.72) and 1.09±0.02(1.07-1.14) in radiotherapy plans for left-sided breast cancer, and 0.65±0.08(0.48-0.76) and 1.09±0.04(1.03-1.18) in radiotherapy plans for right-sided breast cancer, respectively. Conclusions CTR, CLD, and MHD can predict the rationality of each parameter in IMRT planning for left-sided breast cancer rather than right-sided breast cancer. The obtained formulae can help physicians choose the optimal setting mode for radiation field and improve the quality of treatment plans.