A set of techniques to reduce the toxicity of radiation therapy for locally advanced rectal cancer

Abstract

In order to reduce the incidence of acute radiation toxicity during chemoradiation therapy in patients with rectal cancer, we proposed a prone position for patient on the treatment table using a BellyBoard fixation device. The data on 156 patients with rectal cancer who underwent radiation therapy were analyzed, 108 patients were treated in prone position, 48 patients were treated in supine position. We obtained data on the reduction of small intestine volumes treated with the calculated dose of 35, 40 and 45 Gy (V35, V40 and V45) when positioning in the prone position compared to positioning in the supine position when contouring the volume of the small intestine in a single block (bowelbag). Treatment in the prone position using a BellyBoard fixation device significantly reduced acute urogenital toxicity (by 30%) and significantly reduced the incidence of grade 2 cystitis by 4 times (from 12% to 3%) compared with treatment of the patient in supine position. Treatment in the prone position using a BellyBoard significantly reduced the incidence of grade 3 enterocolitis by 5 times (from 10% to 2%) compared with treatment of the patient in supine position. Despite a number of objective advantages of using a BellyBoard fixation device, treatment in prone position is associated with a decrease in the reproducibility of patient positioning compared to supine position. The main source of error when using a BellyBoard is the unstable position of its aperture relative to the patient's anatomy. Treatment in prone position, planning using intensity-modulated radiation therapy (IMRT) and volume-modulated arc radiation therapy (VMAT), determining the indents during the conversion from the clinical target volume (CTV) to the planned target volume (PTV) based on the analysis of interfractional displacements, determining the optimal multiplicity of visual control may help to reduce the acute toxicity of chemoradiotherapy in patients with local advanced rectal cancer.