Implication of Bifurcation of Abdominal Aorta for Radiotherapy Planning for Cervical Cancers.

Abstract

External Beam Radiotherapy plays a major role in the management of Carcinoma Cervix. The Radiotherapy treatment portals are designed to adequately cover the gross disease and areas of microscopic spread. The upper border of Radiotherapy field is traditionally placed at the level of L4-L5 intervertebral space to cover the common iliac nodal area. It is determined based on anatomical and surgical series which have shown that division of Abdominal aorta occurs at that level. To study the level of the division of abdominal aorta in relation to the lumbar vertebral levels. To propose the change in the upper border of Radiotherapy portals used in the treatment of Cervical Cancers. Patients who underwent Radiotherapy for Cervical Cancer from December 2010 to January 2012 formed the subjects of this prospective study. All the patients underwent aquaplast immobilization in supine position and contrast enhanced Computed Tomography (CT) simulation for Radiotherapy planning following bladder protocol. The Radiotherapy planning was done on commercial treatment planning system, Prowess version 4.71. The level of division of Abdominal Aorta into right and left Common Iliac arteries with respect to vertebral level was determined and studied. The division of abdominal aorta into common iliac arteries occurred at the level of L3-L4 intervertebral space, in front of body of L4 vertebra and L4-L5 intervertebral space in 53.84%, 30.76% and 15.40% of the patients respectively. The division of abdominal aorta occurs at a higher level than L4-L5 intervertebral space in majority of patients. It is highly recommended to use CT scan based planning. However, in institutes where there are no facilities for CT based planning, it is advisable to shift the upper border of Radiotherapy treatment portal above the L3-L4 intervertebral space for delivering adequate doses to the common iliac lymphnodes.