The aim of this study was to evaluate the dosimetric variations of static intensity-modulated radiotherapy (sIMRT), dynamic intensity-modulated radiotherapy (dIMRT) and volumetric modulated arc therapy (VMAT) for thoracic esophageal cancer (EC). Ten patients with pathologically-confirmed
EC were randomly selected. The Monaco 5.11 treatment planning system was used to design six radiotherapy plans, namely sIMRT with 5 fixedfields (S5) and 7 fixed-fields (S7), dIMRT with 5 fixed-fields (D5) and 7 fixed-fields (D7) and VMAT plan with single arc (VMAT1) and double arc (VMAT2),
respectively. The dosimetric parameters were compared among six different plans. The dose to target volumes met the clinical prescription requirements in all six plans. The D5 plan had the lowest dose exposed to the whole lungs, except for V5, which was only 1.7% higher than that
in the D7 plan. The low dose to lungs (V5 and V10) in VMAT plans (VMAT1 and VMAT2) were higher than in IMRT plans, but the statistical differences were significant (P < 0.05) only in comparison with dynamic IMRT plans (D5 and D7). The V20 and V30
of lungs in VMAT2 plan were also higher than that in other plans, but the statistical differences were significant (P < 0.05) only in comparison with D5 plan. The doses delivered to the spinal cord and heart showed no statistical significance (P > 0.05). The monitor units
(MUs) and treatment time (TT) significantly increased with the increasing number of fields in the same kind of fixed-fields IMRT plans (S5 vs. S7; D5 vs. D7). The MUs in VMAT plans, especially in VMAT2, increased significantly (P < 0.05) when compared with sIMRT and 5-fields dIMRT
plans, respectively. VMAT1 plan had the shortest TT and the highest delivery efficiency. For thoracic esophageal cancer, the D5 plan can shorten the TT and improve the delivery efficiency while meeting the dosimetric requirements and sparing the lungs. VMAT can significantly reduce the TT,
but at the expense of increasing the dose to lower-dose regions of lungs, which means VMAT plan may not shows obvious dose advantage for thoracic esophageal cancer.
Dosimetric comparison between modulated arc therapy and static intensity modulated radiotherapy in thoracic esophageal cancer: a single institutional experience
