Correlation between displacement of GTV and volumetric parameters of primary tumor in thoracic esophageal cancer based on repeated 4DCT scans during radiotherapy

Abstract

Objective To investigate the correlation between the displacement of gross tumor volume (GTV) and the volume,length,and largest diameter of primary tumor in thoracic esophageal cancer based on repeated enhanced four-dimensional computed tomography (4DCT) scans during fractionated radiotherapy.Methods Thirty enrolled patients with thoracic esophageal cancer underwent enhanced 4DCT scans before radiotherapy and every ten fractions during radiotherapy.The displacements of GTV in left-right (LR),anterior-posterior (AP),and superior-inferior (SI) directions in each scan were obtained,and then the correlation between the displacements and the volume,length,and largest diameter of primary tumor was analyzed.Results In the 20th fraction,a significant positive correlation was observed between the displacement of GTV in LR direction and the volume of primary tumor for all patients and the patients with lower-thoracic esophageal cancer (P =0.012 and 0.040),between the displacement of GTV in SI direction and the length of primary tumor for all patients and the patients with upper-and middle-thoracic esophageal cancer (P =0.003,0.031,and 0.044),and between the displacement of GTV in LR direction and the length of primary tumor for the patients with lower-thoracic esophageal cancer (P =0.027).At the first 4DCT scan before radiotherapy,a significant positive correlation was observed between the largest diameter of primary tumor and the displacement of GTV in LR and SI directions and three-dimensional vector for all patients (P=0.036,0.033,and 0.018) and between the largest diameter of primary tumor and the displacement of GTV in LR direction for the patients with lower-thoracic esophageal cancer (P =0.011).Conclusions In different fractions of radiotherapy,no significant correlation is found between the displacement of GTV in AP direction and the volume,length,and largest diameter of primary tumor in patients with lower-,middle-,or upper-thoracic esophageal cancer.However,their correlation with the displacement of GTV in LR and SI directions depends on the location of tumor and fraction of radiotherapy. Key words: Esophageal neoplasm/radiotherapy; Tomography, X-ray computed, four-dimensional; Gross tumor volume; Correlation of target displacement