单侧乳腺癌放疗中健侧乳腺受照剂量及其诱发癌症风险预测

Estimated radiation dose and breast cancer incidence risk of contra-lateral breast for patients with unilateral breast cancer

目的 分析单侧乳腺癌放疗所致健侧乳腺的剂量，并估算放疗诱发健侧乳腺癌的风险。方法 在同一医院调查49例接受单侧乳腺放疗患者的基本情况，从治疗计划系统上获取其健侧乳腺的辐射剂量并进行统计分析；利用美国电离辐射生物效应委员会报告Ⅶ第2部分（BEIR Ⅶ phase 2）推荐的风险模型，结合我国人口寿命表，预测不同年龄段单侧乳腺癌患者接受放疗诱发健侧乳腺癌的风险。结果 患者的处方剂量均为50 Gy，健侧乳腺的平均剂量为（1.21±0.89）Gy （0.14～3.59 Gy），最大点剂量平均为（17.42±13.20）Gy （0.98～45.27 Gy）；健侧乳腺的最大点剂量和平均剂量变化幅度大，且有显著相关性（R=0.527，P=0.000），不同年龄段患者的健侧乳腺平均剂量差异无统计学意义（P〉0.05）。基于健侧乳腺的平均剂量，估算出受照年龄为35、40、50、60、70和80岁患者的健侧乳腺癌终生归因风险分别为2 449/10万人、1 857/10万人、994/10万人、446/10万人、173/10万人和55/10万人。结论 患者接受单侧乳腺癌放疗过程中，其健侧乳腺剂量可达1 Gy水平，可能增加健侧乳腺癌发生风险对年轻患者不容忽视，在制定放射治疗计划时应尽可能控制对患者健侧乳腺的照射。

Objective To analyze the radiation dose to contra-lateral breasts and estimate the incidence risk of contra-lateral breast cancer for women undergone unilateral breast cancer radiotherapy. Methods The radiation doses of contra-lateral breasts for 49 patients were counted and analyzed in a hospital, and the risk of contra-lateral breast cancer in different age groups that induced by radiotherapy was estimated based on BEIR Ⅶ model combined with the Chinese lifetime table. Results The prescribed doses for the patients were all 50 Gy. The mean dose to contra-lateral breasts ranged from 0.14 Gy to 3.59 Gy, with an average of （1.21±0.89） Gy, and the maximum point dose varied from 0.98 Gy to 45.27 Gy, with the average of （17.42±13.20） Gy. Both the maximum point dose and the mean dose obviously varied among the patients, and their correlation was significant （R=0.527,P=0.000）. Furthermore, no significant differences of the mean dose was found among the ages （P〉0.05）. The lifetime attribute risks of contra-lateral breast cancer were estimated to be 2 449, 1 857, 994, 446, 173 and 55 for per 100 thousand women corresponding to the ages of 35, 40, 50, 60, 70 and 80, respectively. Conclusions In the radiotherapy for unilateral breast cancer, the dose delivered to the contra-lateral breast is about 1 Gy order of magnitude, the risk of contra-lateral breast cancer cannot be ignored for young women. Therefore, the irradiation dose of contra-lateral breasts should be controlled as less as possible in planning the treatment.