Comparison of nodal irradiation dose using radiotherapy for patients with thoracic esophageal cancer.

The present study aimed to compare incidental nodal irradiation (INI) doses using volume-modulated arc therapy (VMAT), 5-field intensity-modulated radiotherapy (5F-IMRT) and 3D-conformal radiotherapy (3D-CRT) treatment plans for patients with thoracic esophageal cancer (EC). A total of 15 patients with thoracic EC were selected for participation between October 2016 and July 2017 at the Hangzhou Cancer Hospital. Regional lymph nodal stations were contoured according to 3D CT-based images of the Japan Esophageal Society Guidelines. All patients were treated with 60 Gy using VMAT, 5F-IMRT and 3D-CRT plans. Dose-volume histograms of planning target volume (PTV), lung, heart, spinal cord and incidental nodal irradiation were compared between the three plans. 5F-IMRT was superior in PTV_V95% (the volume of the PTV receiving 95% of the prescription dose, P=0.003) and the VMAT plan was best in terms of conformal index (P=0.005). V20 and V30 were reduced by 10.7-22.6% (P=0.002) and 12.8-21% (P=0.026), respectively, in normal lung tissue using the VMAT plan. 5F-IMRT demonstrated the lowest maximum dose (Dmax) for the spinal cord (P=0.037). For the INI, 3D-CRT exhibited the highest equivalent uniform dose (EUD) values for 106pre (P=0.014) and 106tb-L (P=0.03) in upper-thoracic EC. The mean EUD of all lymph nodal regions in middle-thoracic EC were >40 Gy in VMAT and 5F-IMRT plans; the VMAT plan had higher EUD values in lower-thoracic EC compared with 5F-IMRT, 3D-CRT plans for INI. VMAT were comparable to the 5F-IMRT plan with respect to dosimetric characteristics for planning and INI doses to thoracic nodal levels NO 105-112 are considerable for thoracic EC.