Simultaneous integrated boost (SIB) of the parametrium and cervix in radiotherapy for uterine cervical carcinoma: a dosimetric study using a new alternative approach

Objective:To compare the dose distributions of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) using the simultaneous integrated boost (SIB) technique with that of the traditional midline block (MB) technique for boosting the parametrium in patients with cervical cancer.Methods:Treatment plans using VMAT or IMRT with the SIB technique (VMAT-SIB and IMRT-SIB) and IMRT followed by the MB technique (IMRT-MB) were generated for each of the 10 patients with cervical cancer. For the SIB plans, 45-Gy and 50-Gy dose levels in 25 equal fractions were set for the pelvis planning target volume 45 (PTV45) and the parametrial boost volume (PTV50), respectively. For the IMRT-MB plans, the parametrium was sequentially boosted with the MB technique (5.4 Gy in three fractions) after pelvic IMRT (PTV45).Results:Volume receiving 100% of the prescribed dose or more coverage of the PTV50 was significantly better for VMAT-SIB and IMRT-SIB than that for IMRT-MB (99.08 and 99.31% compared with...