左侧乳腺癌保乳术后三维适形光子放射治疗、调强光子治疗和质子治疗的剂量学比较

Dosimetric comparison of 3D conformal conventional photon plan,intensity modulated photon plan and proton plan in the treatment of the left-sided breast cancer

目的比较左侧乳腺癌保乳术后三维适形光子放射治疗技术、调强光子治疗技术和质子治疗技术的靶区剂量分布和正常组织受照剂量的差异。方法7例左侧乳腺癌保乳术后的患者，CT定位扫描，勾画靶区和周围正常组织，分别制定三维适形光子放射治疗计划、调强光子治疗计划和质子治疗计划。处方剂量50Gy／25F／5W。比较3种不同治疗技术靶区的剂量分布和周围正常组织的受照剂量。结果3种不同治疗技术的靶区剂量分布是相似的，但是质子治疗技术的适形指数好于非质子治疗计划。质子治疗技术正常组织的受照剂量明显低于非质子治疗技术。结论质子治疗技术在保持靶区剂量分布均匀的同时，可以明显减少周围正常组织的受照剂量。

Objective To compare,using different treatment techniques with 3D conformal conventional photon beams, intensity modulated photon beams and proton beams for postoperative whole breast radiotherapy for left-sided breast cancer patients, the dose delivered to ipsilateral lung, contralateral breast and heart. Methods Seven left-sided breast cancer patients were selected for this comparative study. CT scan was performed covering the entire chest. CTV was contoured on the relevant sclices. PTV was contoured from CTV adding a 0. 5 nun margin all directions, and no closer than 5 mm to the skin surface, no deeper than the anterior chest wall. For each of patients,3D conformal conventional two-field tangential photon plan, two-field intensity modulated photon plan and one or two-field proton plan were calculated using Varian Eclipse treatment plan system. PTV coverages were comparable among the different treatment techniques. Results The prescribed dose to 95% of the PTV was 50Gy. The doses to neighbouring organs were compared. The mean doses delivered to the ipsilateral lung for 3D conformal conventional photon plans, IMRT plans and proton plans were 494. 7 ± 200. 9cGy ,455.3 ± 188.7 cGy and 27. 3 ± 26. 5cGy, respectively. The mean doses delivered to the contralateral breast were 81.9 ± 17.3cGy,77.0 ±21.7cGy and 0. 2 ±0. 2cGy,respectively. The mean doses delivered to the heart were 396. 7 ± 131.6cGy,376.0 ± 124. 9cGy and 0.9 ± 1.0cGy,respectively. Conclusion Compared to non-proton plans, proton plans significantly reduced the doses delivered to neighbouring organs.