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

Abstract

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 iliac lymph nodes were delineated on the plan.ning 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 L 4 ;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 iliac 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 de-fined as adequate, undersize and oversize when the distances were 15-20 mm, less than 15 mm and more than 20 mm, respectively. Results Superiorly, the common iliac lymph nodes were missed in 98% pa-tients, 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. Key words: Cervical neoplasms/radiotherapy; Tomography; X-ray computed; Lymph nodes; overlay