Dosimetric comparison between volumetric modulated arc radiotherapy and five fields intensity-modulated radiation therapy for postoperative cervical carcinoma

Abstract

Objective To determine the dosimetric differences between volumetric modulated arc radiotherapy(VMAT) an five fields intensity-modulated radiation therapy(5F-IMRT) for postoperative cervical cancer. Methods Ten patients with postoperative cervical carcinoma were enrolled in this study. Single arc VMAT, double arc VMAT, and 5F-IMRT plans were generated for these patients. Dose of target, conformal index (CI), homogeneity index (HI), organs at risk and monitor units (MU) were analyzed. The measurement data were analyzed by single factor analysis of variance, and an LSD test was performed in both two groups. Results Single arc and double arc VMAT plans both satisfied the clinical dosimetriy requirements. No significant difference was observed between the VMAT and 5F-IMRT plans with respect to the maximum dose(Dmax) of the target, mean dose(Dmean), CI, and HI. Compared with these plans, the single arc VMAT was weaker and significantly different with respect to the above-mentioned variables (F=24.102, 13.710, 5.919, 11.045, all P 0.05). The MU values o f the single arc and double arc VMAT plans were significantly lower than that of 5F-IMRT(F=295.138, P>0.05). Meanwhile, significant difference was observed between the Dmax values of the small intestine, rectum, and bladder for double arc VMAT plan, single arc VMAT plan and those of the 5F-IMRT plan(F=16.069, 7.521, 13.966, all P<0.05). The bladder V20, V30 and V40 for 5F-IMRT were better than those of the single arc and double arc VMAT, and the differences were significant(F=5.142, 20.095, 7.387, all P<0.05). The left femoral head V20 and V30 for single arc and double arc VMAT plan was superior to that of 5F-IMRT, and the differences were statistically significant (F=3.717, 16.040, both P<0.05). The right femoral head V30 and V40 for single arc and double arc VMAT plan was superior to that of 5F-IMRT, and the differences were statistically significant (F=10.873, 7.791, both P<0.05). Conclusions Compared with 5F-IMRT, the double arc VMAT achieved equal dosimetric parameters with fewer MU. In terms of organ at risk protection, the three plans have their own advantages, but the MU of the VMAT plan is significantly reduced, which can improve the treatment efficiency and worth further study. Key words: Uterine cervical neoplasms; Volumetric modulated arc radiotherapy; Intensity modulated radiotherapy; Radiotherapy planning; Dosimetrics