[Dosimetric study of postoperative 3-dimensional conformal radiotherapy and coplanar decile intensity-modulated radiotherapy for cervical cancer].

OBJECTIVE: To compare the difference of the dose distribution in clinical target volume and organ at risk (OAR) between coplanar decile field intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy (3D-CRT) for postoperative radiotherapy of cervical cancer.

METHODS: Ten postoperative patients with cervical cancer were selected randomly to undergo CT scan and planning target volume (PTV) and OAR contouring. 3D-CRT and coplanar decile IMRT planning was performed for each patient with a prescribed dose of 50 Gy. The homogeneity index (HI), conformity index (CI), maximum dose, minimum dose, mean dose of PTV, and irradiated volume of OARs were calculated and the results were compared.

RESULTS: 5-field IMRT, 7-field IMRT and 9-field IMRT plans had a significant better conformity index (CI) of PTV compared with 3D-CRT (P<0.05) . Compared with 3D-CRT plans , V30, V40, and V50 of the bladder, V50 of the small bowel, and V30, V40, and V50 of the rectum in the coplanar decile IMRT plans were all significantly reduced (P<0.05) but showed no significant differences among the IMRT plans (P>0.05).

CONCLUSION: Coplanar decile IMRT plans is superior to 3D-CRT plan in terms of the conformity index (CI) of the PTV and sparing the bladder, rectum and small bowel. Seven-field and 9-field IMRT do not warrant more benefits than 5-field IMRT, and the latter can significantly reduce the treatment time and costs.