Preliminary study of the internal margin of the gross tumor volume in thoracic esophageal cancer

Abstract

PurposeTo measure the displacement of the tumor of the gross tumor volume (GTV) of thoracic esophageal cancer in the calm states of end-inspiration and end-expiration for determining the internal margin of the GTV (IGTV). MethodsTwenty-two patients with thoracic esophageal cancer who were unable to undergo surgery were identified in our hospital. The patients received radiotherapy. By using 16-slice spiral computed tomography (CT), we acquired the calm states of end-inspiration and end-expiration. The displacement and volume changes in tumor target volume were measured, and the changes were analyzed to determine if these were associated with the tidal volume and the location and length of the target volume V. In the end, we analyzed the displacement of tumor target volume and calculated the internal margin of the GTV by empirical formula. ResultsThe average tidal volume was 463.6ml. The average GTV at end-inspiration was 33.3ml and at end-expiration was 33.35ml. Three was not any significant between two groups (T=−0.034, P>0.05). The IGTV (X-axis direction) was 3.09mm for the right sector and 4.08mm for the left border; the IGTV (Z-axis direction) was 3.96mm for the anterior border and 2.83mm for the posterior border; and the IGTV (Y-axis direction) was 7.31mm for the upper boundary (head direction) and 10.16mm for the lower boundary (feet direction). The motion of the GTV showed no significant correlation with the tidal volume of patients and the length of the tumor, but in relation to the tumor location, the displacement of the lower thoracic and the middle thoracic target volumes occurred in the direction of the anterior and right, which were not significantly different (T=0.859, 0.229, P>0.05) The significant differences were observed for the other directions (P<0.05). ConclusionsBecause of respiratory and organ movements, the displacement of the tumor target volume was different in all directions. Therefore, we recommend that expansion of the planning target volume during clinical radiation treatment needs to include the displacement of the tumor target volume caused by respiratory and organ movements during each radiotherapy session.