Intra-fractional dosimetric analysis of image-guided intracavitary brachytherapy of cervical cancer.

Abstract

BACKGROUND:

To assess the intra-fractional dosimetric variations of image-guided brachytherapy of cervical cancer.

METHODS:

A total of 38 fractions (9 patients) undergoing brachytherapy for cervical cancer underwent a CT scanning for treatment planning (planning CT) and a Cone-beam CT (CBCT) scanning immediately prior to delivery (pre-delivery CBCT). The variations of volumes as well as the dosimetric impact from treatment planning to delivery (intra-application) were evaluated. The dose volume histogram parameters including volume, D90 of high-risk clinical target volume (HRCTV) and D2cc of organs at risk (OARs) were recorded.

RESULTS:

The relative differences (mean ± 1SD) of the volume and D90 HRCTV across the two scans were - 2.0 ± 3.3% and - 1.2 ± 4.5%, respectively. The variations of D2cc for bladder, rectum, sigmoid and small intestine are - 0.6 ± 17.1%, 9.3 ± 14.6%, 7.2% ± 20.5% and 1.5 ± 12.6%, respectively. Most of them are statistically nonsignificant except the D2cc for rectum, which showed a significant increase (P = 0.001). Using 5% and 10% uncertainty of physical dose for HRCTV at a 6 Gy × 5 high-dose-rate schedule, the possibility of total equivalent doses in 2 Gy fractions (EQD2) lower than 85 Gy is close to 0% and 3%, respectively. Performing similar simulation at 15% and 20% uncertainty of a 4 Gy physical dose for OARs, the possibility of total EQD2 dose exceeding 75 Gy is about 70%. Less than 1% of the total EQD2 of OARs would exceed 80 Gy.

CONCLUSIONS:

Average intra-fractional dosimetric variation of HRCTV was small in an interval of less than 1 h, and the possibility of total EQD2 exceeding 85 Gy is higher than 97%. The intra-fractional dosimetric variations of OARs might result in an overdose for OARs in a single fraction or the whole treatment. It is necessary to detect unfavorable anatomical changes by re-imaging and take interventions to minimize applied doses and reduce the risk of complications.

• Authors: Junfang Yan, Jiawei Zhu, Kai Chen, Lang Yu, Fuquan Zhang
• Journal: Radiation oncology (London, England) (Radiat Oncol) Vol. 16 Issue 1 Pg. 144 (Aug 04 2021) ISSN: 1748-717X [Electronic] England
• PMID: 34348758 (Publication Type: Journal Article)
• Copyright: © 2021. The Author(s).

Topics

• Brachytherapy (methods)
• Cone-Beam Computed Tomography (methods)
• Female
• Follow-Up Studies
• Humans
• Organs at Risk (radiation effects)
• Prognosis
• Radiotherapy Dosage
• Radiotherapy Planning, Computer-Assisted (methods)
• Radiotherapy, Image-Guided (methods)
• Radiotherapy, Intensity-Modulated (methods)
• Uterine Cervical Neoplasms (diagnostic imaging, pathology, radiotherapy)