宫颈癌常规照射野对盆腔淋巴结覆盖性研究

Coverage of pelvic lymph nodes in conventional pelvic radiation for cervical cancer

目的应用CT模拟定位技术勾画盆腔淋巴结靶区，评估宫颈癌常规盆腔照射野对淋巴结靶区覆盖性。方法选择56例宫颈癌患者进行CT模拟定位，在CT图像上勾画髂总、髂内、髂外淋巴结区域。在冠状、矢状位的数字重建图像上复制出常规盆腔4个野照射边界：前后野上界为L4下缘，下界为闭孔下缘，左、右侧界为真骨盆外各15mm；侧野上下界同前后野的上下界，前界为耻骨联合最前缘，后界为骶骨后缘。分别测量野的上界至腹主动脉分叉的距离，野的上界至髂总动脉分叉的距离，前后野的侧界至最近的髂外动脉的距离，侧野的前界至最近的髂外动脉的距离。定义血管壁至射野距离在15～20mm为射野大小充分，〈15mm为射野过小，〉20mm为射野过大。结果上界98％患者有髂总淋巴结遗漏，2％患者射野过大；14％患者至少有一侧髂内、外淋巴结遗漏。侧界41％患者有髂外淋巴结遗漏，11％患者射野过大。前界43％患者有髂外淋巴结遗漏，25％患者射野过大。结论根据骨性标记定义常规盆腔照射可能带来淋巴结靶区遗漏（特别是髂内外淋巴结），用CT或MRI图像勾画淋巴结靶区可以个体化设计照射野，以保证淋巴引流区包括在照射野内。

Objective To assess the coverage of pelvic lymph nodes in conventional pelvic radiation for cervical cancer. Methods Between Jan. 2005 and Mar. 2008, 56 patients with cervical cancer receiv- ing radiotherapy were enrolled in this study. The common iliac, external and internal iliae lymph nodes were delineated on the plann.ing CT images. The borders of conventional pelvic irradiation fields were copied to the sagittal and coronal images of digital reconstruction. Anterior-posterior fields （AP） ：superior border was the inferior border of L4 ; inferior border was the inferior border of the obturator foramen; and lateral borders were 15 mm lateral to The bone pelvic. Lateral fields （LAT） ：anterior border was anterior to the symphysis pubis; posterior border was the posterior border of the sacrum. Distances were measured between the bifurcation of the aorta and superior border, between the bifurcation of the common iliae artery and lateral border of the AP field, and between the external iliac artery and anterior border of the LAT field. The radiation fields were defined as adequate, undersize and oversize when the distances were 15 -20 mm, less than 15 mm and more than 20 ram, respectively. Results Superiorly, the common iliac lymph nodes were missed in 98% patients, oversize fields found in 2%, and at least one side of the internal or external iliac lymph nodes missed in 14%. Laterally, the external iliac lymph nodes were missed in 41% patients, and oversize fields found in 11%. Anteriorly, the external iliac lymph nodes were missed in 43% patients, and oversize fields found in 25%. Conclusions Conventional pelvic radiation fields according to the bone markers may miss the pelvic lymph nodes, especially the internal iliac lymph nodes. The target nodes should be delineated individually based on CT or MRI to guarantee their coverage in radiotherapy.