Impact of contrast-enhanced 4DCT scan on delineating GTV and constructing IGTV in thoracic esophageal cancer

Objective: To investigate the difference between conventional and contrast-enhanced four-dimensional computed tomography (4DCT) scans in delineating the gross tumor volume (GTV) in different phases and constructing the internal gross tumor volume (IGTV) in primary thoracic esophageal cancer. Methods: Twenty-five patients with thoracic esophageal cancer, including 8 upper-thoracic, 9 middle-thoracic, and 8 lower-thoracic, sequentially underwent conventional and contrast-enhanced 4DCT scans during normal breathing. The GTVs were delineated by a physician under the same standard using conventional plain 4DCT images, and the IGTVs were constructed accordingly. After one month, the GTVs were delineated by contrast-enhanced 4DCT images and IGTVs were constructed by the same physician. Results: The coefficient of variation for the target volume based on the contrast-enhanced 4DCT images was smaller than that based on the plain 4DGT images. There were no significant differences in the length of the z axis of GTV, GTV, and IGTV between contrast-enhanced and plain 4DCT images in patients with upper-and lower-thoracic esophageal cancer (P = 0.529 and 0.110; P = 0.158 and 0.416; P = 0.147 and 0.615). However, in patients with middle-thoracic esophageal cancer, the length of the z axis of GTV, GTV, and IGTV were significantly different between contrast-enhanced and plain 4DCT images (P = 0.005, 0.035, and 0.021, respectively). Conclusions: Contrast-enhanced 4DCT scan can reduce the error in delineating the target volume and construct a more accurate IGTV for patients with middle-thoracic esophageal cancer. However, it has no significant benefit in patients with upper-and lower-thoracic esophageal cancer. (authors)