[Dosimetric comparaison between VMAT and tomotherapy with para-aortic irradiation for cervix carcinoma]

Intensity-modulated radiotherapy (IMRT) has proven its dosimetric superiority over conformational radiotherapy for cervix cancers in terms of digestive toxicity. Volumetric modulated arctherapy (VMAT) has shown its dosimetric interest when compared to IMRT with static beams. The purpose of our study was to compare conformational radiotherapy, VMAT and tomotherapy for cervical cancers with para-aortic lymph nodes irradiation.

The dosimetric data from ten patients were compared between the three techniques, with collection of the dose received by the planning target volume, kidneys, bowel, rectum, bladder, bone marrow and spinal cord, as well as the complete dose.

There was a significant difference in favour of VMAT and tomotherapy when compared with conformational radiotherapy for the organs at risk: intestines (V(20 Gy), V(30 Gy) and V(45 Gy)), rectum (V(30 Gy) and V(45 Gy)), bladder (V(30 Gy) and V(45 Gy)) and kidneys (V(12 Gy), Daverage, V(20 Gy)). Volumes receiving 20, 30 and 45 Gy were significantly higher in conformational radiotherapy than in VMAT and tomotherapy. There was a significant difference in favour of tomotherapy when compared with VMAT for V(12 Gy) in kidneys and V(45 Gy) in the bladder.

This study confirms the interest of VMAT and tomotherapy for pelvic and para-aortic lymph nodes irradiation of cervix cancer when compared with conformational radiotherapy. There was little difference between VMAT and tomotherapy, except for kidney sparing, which was better with tomotherapy and thus may be interesting for patients receiving nephrotoxic chemotherapy.