Respiratory motion of GTV and its influential factors in patients with primary thoracic esophageal cancer

Abstract

Objective To investigate the three-dimensional (3D) motion of gross tumor volume (GTV) and its influential factors in patients with primary thoracic esophageal cancer based on fourdimensional CT (4DCT).Methods Sixty-five patients with thoracic esophageal cancer underwent 3DCT and 4DCT simulation scans during normal breathing to measure the centroid motions of GTV in the left-right (LR),anterior-posterior (AP),and superior-inferior (SI) directions.The distances from the upper and lower edges of GTV to the lower edges of the aortic arch and tracheal carina and the diaphragmatic dome at both sides were measured.The patients were grouped based on age,sex,and the location,pathological type,volume,and length of tumor.The impacts of the above factors on GTV motion and the correlation between the positions of tumor upper/lower edges and GTV motion were analyzed.Results The centroid motions of GTV in the LR,AP,and SI directions were 0.15 cm,0.12 cm,and 0.34 cm,respectively.The patients with lower thoracic esophageal cancer had lager centroid motions of GTV in the LR and AP directions than those with upper and middle thoracic esophageal cancer (P =0.036 and 0.014),but there was no significant difference in the centroid motion of GTV in the SI direction (P =0.123).There were no relationships between GTV motion and the sex,age,and body mass index (BMI) of patients (PLR =0.464,0.962,and 0.727,PAP =0.924,0.594,and 0.865,PSI =0.955,0.264,and 0.139).A significant difference was found between patients with different tumor lengths in terms of the GTV motion in the LR direction (P =0.014).GTV motions were not correlated with whether lymph node metastasis occurred (P =0.502,0.665,and 0.815),but they were negatively correlated with the distances between the upper and lower edges of GTV and the tracheal carina (P =0.000-0.014).Conclusions The maximum GTV motion is seen in the SI direction among patients with thoracic esophageal cancer during normal breathing.Age,sex,BMI,and mediastinal lymph node metastasis have no impacts on target volume expansion,and appropriate site-specific internal target volume expansion should be determined in consideration of the tumor location and the distances between the upper and lower edges of GTV and the tracheal carina. Key words: Esophageal neoplasms/radiotherapy; Tomography, X-ray computed, four-dimensional; Target displacement ; Influencing factors