Planning Study For Esophageal Cancer: A Dosimetric Comparison Of Conformal Radiation Therapy, Vmat, And Hybrid-Vmat

The aim of this study was to compare dosimetric parameters of conformal radiotherapy (CRT), volumetric modulated arc therapy (VMAT) and Hybrid-VMAT (Hy-VMAT) plans for the treatment of patients with esophageal cancer. Twenty treatment plans were generated by means of each dose delivery technique using a commercial planning system (Eclipse; Varian Medical Systems). Respective dose prescriptions were 40 and 20 Gy for the PTVelective and PTVboost (2Gy/ fraction). For CRT, doses were prescribed at isocenter. For VMAT and Hy-VMAT, doses were prescribed at the mean dose of PTV. The CRT plans consisted of opposite two fields (anterior-posterior, AP) to deliver prescription dose to the isocenter. The VMAT plans used 2 full arcs while lateral treatment beams (250-290° and 70-110°) were turned off to minimize doses to the lung tissue. The most of the doses were delivered with VMAT, and 30 % were delivered in antero-posterior (A-P) directions in Hy-VMAT. Dosimetric parameters of the PTV and surrounding organs at risk (OARs) were compared. All plans had sufficient in Dmean and D2 of PTV, no significant differences were observed except D98 of PTV. The lung V5, V20 and Dmean were 45.6 ± 14.6%, 19.3 ± 8.1% and 10.0 ± 2.8%, in CRT, 64.5 ± 19.8%, 10.1± 4.4%, and 9.4± 2.6% in VMAT and 57.3± 15.4%, 9.3 ± 4.2%, and 8.6± 2.4% in Hy-VMAT, respectively. The doses of lung except V5 were lower in Hy-VMAT. The Dmax of Spinal cord was lower in VMAT than in other plans. Regarding the dose coverage of the PTV, there was no significant difference except D98 of PTV in the three treatment techniques. The larger the size of PTV is, the greater the lung V5 trends to. VMAT and Hy-VMAT can decrease the volume of lung receiving high doses, but increase low doses to lung. In comparison to VMAT, Hy-VMAT is a useful scheme that decreases dose of lung and heart.Abstract 3663Doses of OARsLungV5V20DmeanHeart V40Cord DmaxCRT45.6±14.619.3±8.110.0±2.872.0±6.041.9±8.7VMAT64.5±19.810.1±4.49.4±2.645.7±21.938.5±6.3Hy-VMAT57.3±15.49.3±4.28.6±2.455.5±21.542.0±7.1 Open table in a new tab