First implementation and results of online adaptive radiotherapy for cervical cancer based on CT-Linac combination.

Purpose: To assess the dosimetric effectiveness of image-guided radiation treatment (IGRT) and online adaptive radiation therapy (oART) for cervical cancer. As well as survival follow-up was conducted to validated the safety and efficacy of oART. Methods: A total of 15 cervical cancer patients were enrolled. oART was performed on a CT-integrated linear accelerator. The initial plan was revised to include the distribution of IGRT dose using daily fan-beam CT (FBCT) images, after which the distinctions between ART and IGRT in terms of target coverage and organs at risk (OARs) sparing were analyzed. Survival follow-up was conducted to validated the safety and efficacy of oART in this group. Results: PTV Dmax value decreased by 1.23 Gy in the ART plan when compared to that in the IGRT plan; PTV D95 increased by 1.34 Gy; PTV V50 coverage increased by 4.86%; CTV coverage increased by 3.02%; PTV D2cc of the colon, rectum, and small intestine decreased by 1.24 Gy, 1.29 Gy, and 1.12 Gy, respectively. The V10 and V30 of the pelvis increased by 1.27% and 0.56%, respectively, while the V30 of the left and right femoral heads dropped by 2.82% and 3.41%, respectively. Except for the pelvic changes, all other differences were statistically significant (p < 0.01). The average time for the ART procedure was 21.22 min (range: 18.72-24.90 min). The median follow-up time is 28.0 months. Median event-free survival and overall survival were not reached. EFS rate and OS rate at 3 years were 79.4% and 92.9%. Conclusion: Online ART for cervical cancer can minimize the dose of OARs and enhance the target volume coverage significantly when compared to IGRT with satisfied survival time.