Dosimetric evaluation of image-guided adaptive radiotherapy for locally advanced cervical cancer

This study evaluates the dosimetric benefits of off-line adaptive radiotherapy (ART) planning during radiotherapy for locally advanced cervical cancer. Forty-four patients in our hospital were included. The patients were monitored by cone-beam CT (CBCT), and the secondary CT scanning was performed timely. The ART2 planning was performed based on tumor regression and compared with the initial radiotherapy planning (ART1). The mean time of the secondary CT scanning was the thirteen fractions, and the mean gross tumor volume (GTV) decreased by 23.3%. The ART2 compared with the ART1 planning, significantly reduced the mean dose of PGTV (defined as the GTV with 5 mm expansion all directions)-D2%, V110, and PTV-V110 by 1.9 Gy, 9.2%, and 3.4%, whereas there was no significant difference in tumor target D98%, D50%, and V100 between the two groups. The HI of PGTV and planning target volume (PTV) was significantly lower in the ART2 planning. For the comparison of OARs dosimetric parameters, the ART2 planning was significantly decreased the mean dose of rectum-Dmean (2 Gy), D1cc (0.6 Gy), V30 (7.3%) and V40 (5.9%), bladder-D1cc (1.1 Gy), left femoral head-Dmean (1.2 Gy), V40 (1.3%) and right femoral head-Dmean (1.3 Gy), but significantly increased the small intestinal-V30 (2.5%). Other OARs dosimetric parameters were similar between two plannings. The Off-line ART planning can adapt for the changes in the target volume, and further decrease the target volume hotspot area/dose and OARs irradiation dose in locally advanced cervical cancer patients. And the clinical benefit of ART still needs to be verified in clinical trials.