Comparisons of dose distributions between IMPT and VMAT for pancreatic cancer / 中华放射医学与防护杂志

ABSTRACT

Objective:To compare dose distributions of hypofractionated radiotherapy for pancreatic cancer between IMPT and VMAT.Methods:Ten pancreatic cancer cases were included in this retrospective study. Photon (Edge) and proton (Proteus?PLUS) plans were designed by Eclipse and RayStation TPS, respectively. All plans were transferred to MIM system for extraction of parameters, which included Dmin, Dmean and Dmax of PTV, conformity index (CI), new conformity index (nCI), homogeneity index (HI), gradient index (GI), coverage, Dmax and dose-volume of the organs at risk (OARs). Results:There was no significant difference in CI between the two groups. The higher PTV Dmin, Dmean, Dmax, D98%, D2%, HI, coverage and the better GI, D2 cmwere found in VMAT ( t/ Z=-4.63-5.32, P<0.05). The lower 10%_PD was found in IMPT ( t=-7.47, P<0.05). Regarding the OARs, Dmax of the intestine, stomach, and duodenum and Dmean of the left kidney were similar between two groups without significant difference ( P>0.05). The D5 cm 3 of the intestine, D10 cm 3 of the stomach, D5 cm 3 and D10 cm 3 of the duodenum, D2/3 of the left kidney, Dmean and D2/3 of the right kidney were lower in IMPT than those in VMAT ( t/ Z=-8.12--2.60, P<0.05). However, the Dmax and D0.35 cm 3 of the spinal cord were higher in IMPT than those in VMAT ( t=7.30, 6.77, P<0.05). Conclusions:Both of hypofractionated radiotherapy plans of pancreatic cancer designed by VMAT and IMPT could meet clinical needs. No significant difference was found in Dmax of the adjacent gastrointestinal tracts between the two groups. While IMPT had the advantage over VMAT in the case of lower dose-volumes of the gastrointestinal tracts. Nevertheless, less protections of the OARs in front of the tumor volume could be provided by IMPT compared with VMAT.