乳腺癌锁骨上区IMRT和3D-CRT放疗技术甲状腺剂量学比较研究

Comparative study of thyroid dosimetry during intensity modulated radiotherapy and three-dimensional conformal radiotherapy for breast cancer on the supraclavicular area

目的随着放疗技术的进步和颈部放疗剂量的增加,乳腺癌患者甲状腺功能减退发生率明显增加,本研究通过对比调强放疗(intensity modulated radiation therapy,IMRT)和三维适形放疗(three dimensional conformal radiation therapy,3D-CRT)计划的甲状腺剂量分布关系,探讨哪种放疗技术既能满足临床剂量要求又能更好地保护甲状腺,为制订乳腺癌放疗计划提供一定参考。方法选取甘肃省肿瘤医院放疗科2015-01-01-2017-01-31收治的30例分期为Ⅱ和Ⅲ期,且具有术后放疗适应证的女性乳腺癌患者,按统一射野标准,锁骨上区放疗剂量Dt 50Gy/25f,甲状腺剂量限制参数为V40<45%,同一患者制定IMRT和3D-CRT两种放疗计划,并对两种计划的甲状腺剂量体积进行分组对照研究。结果3D-CRT计划在相同剂量情况下甲状腺剂量分布曲线明显优于IMRT放疗计划;3D-CRT计划较IMRT计划显著降低甲状腺剂量体积,V20(z=-5.353,P<0.001),V30(z=-6.56,P<0.001),V40(z=-6.432,P<0.001);同时3D-CRT计划较IMRT计划显著降低甲状腺最小剂量(z=-6.064,P<0.001)和甲状腺平均剂量(z=-5.87,P<0.001);3D-CRT计划和IMRT计划V50(z=-0.83,P=0.407)剂量体积和甲状腺最大剂量(z=-1.688,P=0.091)差异无统计学意义。结论乳腺癌锁骨上区IMRT放疗计划的锁骨上靶区剂量增高,甲状腺受量增高,而3D-CRT放疗能满足临床治疗要求,甲状腺V20、V30、V40和平均剂量低,在甲状腺的保护上具有明显优势。

OBJECTIVE With progress in radiotherapy and increasing dose of radiotherapy in the neck, the incidence of hypothyroidism increased significantly. In this study,we compared the dose distribution of IMRT （intensity modulated radiation therapy） and 3D-CRT （three dimensional conformal radiation therapy） in the thyroid gland to explore which ra- diotherapy techniques meet both clinical dose requirements and better protect the thyroid,providing some guide for breast cancer to the development of radiotherapy. METHODS Selected 30 cases of stage Ⅱ,Ⅲ,and with postoperative radio- therapy indications in women with breast cancer patients, according to uniform field standard,on the supraclavicular radio- therapy dose Dt 50 Gy/25 f, thyroid dose limit parameters： V40 -45%, the same patient to develop IMRT and 3D-CRT two radiotherapy plan,and the two planned thyroid dose volume grouping study. RESULTS 3D-CRT plans significantly decreased thyroid dose V20 （z=- 5. 353, P〈0. 001 ）, V30 （z = -- 6. 56, P〈 0. 001 ）, V40 （ z = - 6. 432, P〈 0. 001 ） ; the 3D-CRT program significantly reduced the minimum thyroid dose （z=-6. 064,P〈0. 001） and the average thyroid dose （z= -5.87, P〈0.001） compared with the IMRT program; and the maximal dose of thyroid （z = -1.688, P = 0.091 ） was not statistically significant （P〈0.05）. There was no significant difference between 3D-CRT and IMRT program V50 （z=-0.83,P=0.407）. CONCLUSION The dose level of supraclavicular target and thyroid gland is increased in IMRT radiotherapy program. 3D-CRT radiotherapy can meet the clinical treatment requirements, V20, V30, V40 and the average dose of thyroid is low and it has obvious advantage in thyroid protection.