Comparison of the ovarian sparing between VMAT and IMRT after ovarian transposition surgery for cervical cancer patients / 中华放射医学与防护杂志

ABSTRACT

Objective:To compare the dosimetric difference between IMRT and VMAT plans for ovarian protection after cervical cancer ovarian transposition surgery.Methods:Thirty-one patients who had received both cervical cancer resection and ovarian transposition were selected for adjuvant radiotherapy. The 9-field evenly divided IMRT and the dual-arc VMAT technology were performed for the treatment planning. The difference of the ovarian mean dose between the two techniques was explored. The relationship between the position of the ovarian-target interval and the ovarian dose was also analyzed.Results:A total of 54 ovaries in 31 patients were effectively transposed and moved out of the target area. Among them, 9 ovaries were located above the upper boundary of the PTV. For these cases, the ovarian mean dose of IMRT and VMAT were (177.8±90.7) and (166.7±70.6) cGy, respectively, which was not statistically different( P>0.05).45 ovaries were located in the same level with PTV. For these cases, the ovarian mean dose of IMRT and VMAT were (459.1±239.9) and (428.3±238.2) cGy, respectively ( z=3.11, P=0.002). The ovarian mean dose has the highest correlation and negative correlation with the closest lateral distance from the ovarian volume center to the PTV surface (IMRT, r=-0.922, P=0.001; VMAT, r=-0.865, P=0.001). To reduce the ovarian mean dose to 500 cGy, the lateral closest distance between the ovarian volume center and the PTV surface should be 3.6 cm and 3.3 cm for IMRT and VMAT respectively. Conclusions:There is no difference between the two planned ovarian doses when the ovaries were located above the upper boundary of the PTV. When the ovaries were located in the same level with PTV, the VMAT plan is better than IMRT in both ovarian dose and treatment efficiency. The ovarian dose could be predicted by the lateral closest distance from the ovarian volume center to the PTV.