乳腺癌改良根治术后CT模拟定位与模拟机定位的剂量学比较

The comparative analysises between CT-simulator and conventional simulator for patients with breast cancer after modified radical mastectomy

目的比较乳腺癌改良根治术后CT模拟定位与模拟机定位(或体表画线)剂量学的差异。方法对83例已行乳腺癌改良根治术拟行放射治疗的患者进行CT模拟定位,同时应用模拟机模拟常规治疗计划,根据剂量-体积直方图(DVH),比较患者采用2种治疗计划的患侧及双肺的V5、V10、V20、V30、计划靶区(PTV)接受40 Gy、45 Gy和50 Gy(PTV40、PTV45、PTV50)的体积百分比、PTV>60、PTV>70的体积百分比及靶区内受照最大剂量(MAX)的差异;比较两种定位模式与患者胸壁厚度的关系,并跟踪随访患者放射性肺炎发生情况。结果患者常规治疗患侧及双肺V5、V10、V20、V30以及PTV40、PTV45、PTV50百分比均小于CT模拟定位计划结果,常规治疗PTV>60、PTV>70的百分比及MAX均大于CT模拟定位计划结果。患者平均胸壁厚度为22.9 mm,常规治疗PTV覆盖及正常组织受量与胸壁厚度呈负相关,CT模拟定位PTV覆盖及正常组织受量与胸壁厚度无相关关系。患者3年随访率达90.4%,放射性肺炎发生率为12.0%(9/75)。结论乳腺癌改良根治术后胸壁电子线照射CT模拟定位靶区涵盖优于模拟机定位的常规治疗计划,肺受量常规治疗计划优于CT模拟定位,但放射性肺炎发生率未见提高。在乳腺癌改良根治术后放射治疗中,CT模拟定位较单纯模拟机定位有明显的优越性。

Objective To compare the dosimetry of CT-simulator and conventional simulator about breast cancer patients after modified radical mastectomy. Method CT-simulator was conducted for 83 breast cancer patients who had received breast modified radical mastectomy, and the conventional treatment was simulated. The dose volume histograms （DVH） were conducted to compare the ratio about V5, V10, V20, V30 of the ipsilateral and bilateral lung and the ratios of target volumes which received the doses for 40 Gy, 45 Gy, 50 Gy （PTV40, PTV45, PTV50）, PTV 〉60, PTV 〉70, the max dose （MAX） in CT-simulator and conventional simulator planning. At the same time, we measured the thickness of the chest wall of the patients, and analyzed the relationships between the thickness of the chest wall and two treatment modes, and followed-up the patients about irradiation pneumonitis. Results The ratios of V5, V10, V20, V30 a- bout ipsilateral and bilateral lung, and PTV40, PTV45, PTV50 for the conventional treatment were less than those for the CT-simulator. The ratios of PTV 〉 60, PTV 〉 70 and MAX were more than those for the CT- simulator. The average thickness of chest wall was 22. 9 mm. There were negative correlations between the thicknesses of the chest wall and the target volume, the doses of normal tissue for the conventional simulator, but no correlations for CT-simulator. The rate of following-up was 90. 4%, and the ratio of irradiation pneumonitis was 12.0% （9/75）. Conclusion The CT-simulator was better than conventional simulator for the patients who had received breast modified radical mastectomy. Though the lung dose of the conventional sim- ulator was better than that for CT-simulator, but the rate of irradiation pneumonitis for CT simulator was not increased. CT-simulator was better than the conventional simulator in breast modified radical mastectomy patients.