Dosimetric superiority of IMRT with jaw tracking technique for whole esophagus and T-shaped field radiotherapy in advanced esophageal cancer.

Abstract

PURPOSE:For whole esophagus and T-shaped field radiotherapy using intensity modulated radiotherapy (IMRT) technique in advanced esophageal cancer, lower absorbed doses to lung and heart remains a challenge. The aim of this study was to investigate the dosimetric superiority in IMRT plans with jaw tracking technique for whole esophagus radiotherapy. METHODS AND MATERIALS:Thirty-two patients with esophageal cancer were subjected to IMRT treatment plans using Eclipse treatment planning system. For every patient, four different plans were generated with six gantry angles: six large fields IMRT plans with fixed jaw (6F-IMRT), six large fields IMRT plans with jaw tracking technique (6F-IMRT-T), twelve small fields IMRT plans with fixed jaw (12F-IMRT), and twelve small fields IMRT plans with jaw tracking technique (12F-IMRT-T). Dosimetric evaluation was assessed for all plans. RESULTS:For every technique, there were no differences in planning target volume (PTV) coverage and conformity. 6F-IMRT-T plans could significantly reduce lung irradiation with 7.9% (P<0.001) reduction in V5lung and 2.5% (P<0.001) reduction in V20 lung respectively compared to 6F-IMRT plans. 12F-IMRT-T plans resulted in superior plans compared to 12-IMRT plans with a reduction of 2.9% (P<0.001) in V5lung and 0.9% (P<0.001) in V20 lung, respectively. For heart irradiation, 6F-IMRT-T and 12F-IMRT-T plans were slightly superior to 6F-IMRT and 12-IMRT plans respectively with a reduction of 1.1 Gy and 0.5 Gy in the respective mean doses. CONCLUSIONS:By the use of jaw tracking technique, the IMRT plans resulted in further lung and heart sparing compared to fixed jaw plans for radiotherapy in esophageal cancer.