两种皮肤通量外扩方法在乳腺癌根治术后调强放疗计划中的剂量学比较

目的:比较两种皮肤通量外扩方法在乳腺癌调强放疗计划中的剂量学差异。方法:对20例左乳腺癌根治术后患者的调强放疗计划分别采用瓦里安Eclipse治疗计划系统（11.0版）提供的Nearest cell（NC）和Erosion-dilation（ED）两种方法进行皮肤通量外扩，生成8FIMRT-NC和8FIMRT-ED计划。比较两组治疗计划的剂量体积直方图、靶区和危及器官的剂量分布、计划验证通过率和单次总机器跳数。结果:两种计划的通量和剂量线均已向胸壁皮肤外扩，两组计划的靶区剂量分布均达到临床处方剂量要求。PTV的最大剂量、平均剂量、大于110%处方剂量受照的体积、适形度指数、均匀性指数、梯度测量值等差异均无统计学意义。主要危及器官肺、心脏和脊髓等的剂量基本相似，差异均无统计学意义。两组计划的验证通过率差异无统计学意义，且均能应用于临床治疗。8FIMRT-ED计划比8FIMRT-NC计划的单次总机器跳数更少，分别为（1 282.35±184.84） MU和（1 302.05±195.37） MU，具有统计学意义（t=2.590, P<0.05）。结论:在乳腺癌根治术后的调强放疗临床计划中，采用NC和ED两种外扩方法均可以将皮肤通量有效外扩，且靶区剂量和危及器官受量均能满足临床治疗要求，两者剂量学无显著差异，但采用ED方法进行外扩，单次总机器跳数更少。

Dosimetric comparison of two kinds of skin fluence expansion methods in intensity-modulated radiotherapy following radical mastectomy for breast cancer

Abstract: Objective To compare the dosimetric differences between two kinds of skin fluence expansion methods in intensity-modulated radiotherapy (IMRT) plan for breast cancer. Methods Twenty patients treated by IMRT after radical mastectomy for left-sided breast cancer were randomly enrolled in the study, and Nearest cell (NC) and Erosion-expansion (ED) provided by Varian Eclipse treatment planning system (Version 11.0) were separately used for skin fluence expansion to generate 8FIMRT-NC plan and 8FIMRT-ED plan. Dose-volume histograms, dose distributions of planning target volume (PTV) and organs-at-risk (OAR), plan verification passing rates and the total monitor units (MU) per fraction were compared between two groups of plans. Results The fluence and dose lines in both groups were expanded to the chest wall skin, and the dose distribution of PTV in both groups met the prescribed dose requirements. There was no significant difference in the Dmax, Dmean, V110%, conformity index, homogeneity index, gradient measurement of PTV between two groups. The doses of the main OAR such as lungs, heart and spinal cord were basically similar, without statistical differences. The difference in plan verification passing rate between two groups was trivial, and both two groups of plans could be applied to clinical treatment. However, the total MU per fraction in 8FIMRT-ED plan was lower than that in 8FIMRT-NC plan, with statistical significance ［(1 282.35±184.84) MU vs (1 302.05±195.37) MU t=2.590, P<0.05］. Conclusion In IMRT after radical mastectomy for breast cancer, both NC and ED can effectively expand the skin fluence, and the dose of PTV and OAR can meet the clinical treatment requirements. There was no significant dosimetric difference between two methods, but the total MU per fraction was less when using ED to expand the skin fluence.