Consideration of doses to some OARs depending on differently chosen CTV margins of lymph nodes in EBRT treatment of the stomach cancer

Based on the computed tomography (CT) images it is not possible to see all the lymph nodes that belong to the stomach. In radiotherapy, for a clinical target volume (CTV) delineation based on CT images, it is necessary to determine the appropriate margin around the corresponding blood vessels to make sure that all the required lymph nodes will be irradiated. The larger margin will certainly cover all the lymph nodes but it can also produce an increase of the received dose in the normal tissues. While a smaller margin can eventually spare the normal structures as a consequence it brings a higher risk of missing the suspected lymph nodes. The aim of this study was to analyse the radiation doses received by some organs at risk (OARs) in the case of the three-dimensional conformal radiotherapy (3DCRT) treatment of the gastric cancer, for lymph node CTV margin sizes 5 mm, 7 mm and 10 mm. The study included 40 patients undergo the external beam radiotherapy (EBRT) treatment of gastric cancer. The one-way analysis of variance (ANOVA) with repeated measures test and Friedman’s nonparametric test have been used for testing the statistical significance of differences among the examined groups. The difference between the examined groups has been considered significant if p < 0.05. The statistically significant differences in the dose contributions to the observed OARs (spinal cord, heart, small bowel and colon), among the examined CTVs, were found.