Incidence of suboptimal applicator placement and the resulting dosimetric impact in image-based intracavitary brachytherapy

Abstract

Aim:With the advent of computed tomography (CT)-based brachytherapy, it is possible to view the appropriate placement of the applicator within the uterine canal and detect uterine perforation. In this study, the incidence of suboptimal placement of the intracavitary applicator and the resulting dosimetric impact were analyzed and compared with a similar set of ideal applicator placement.Materials and Methods:CT datasets of 282 (141 patients) high dose rate brachytherapy insertions between January and April 2016 were analyzed. The target volumes and organs at risk (OAR) were contoured as per the Groupe Européen de Curiethérapie European Society of Therapeutic Radiation Oncology guidelines. The position of the applicator in the uterine cavity was analyzed for each application.Results:The suboptimal insertion rate was 11.7%. There were 26 perforations and 7 subserosal insertions. The most common site of perforation was through the posterior wall of the uterus (42.4%). Fundus perforation and anterior wall perforation were seen in 24.2% and 12.1% of patients, respectively. The average dose to 90% of the target volume (D90 to high-risk clinical target volume) was the highest (9.15 Gy) with fundal perforation. Average dose to 2 cc (D2cc) bladder was highest for fundus perforation (7.65 Gy). The average dose received by 2 cc of rectum (D2cc) was highest (4.49 Gy) with posterior wall perforation. The average D2cc of the sigmoid was highest with anterior perforation (3.18 Gy).Conclusion:In order to achieve better local control and to decrease doses to OAR, it is important to perform a technically accurate applicator placement. A cost-effective, real-time image guidance modality like ultrasound is recommended for all insertions to ensure optimal applicator insertion.

Deformable image registration for dose mapping between external beam radiotherapy and brachytherapy images of cervical cancer

“…In average the deviation was found to be inferior to 5% but large uncertainties were observed for individuals with a standard deviation superior to 20%. Such D2cc deviations can mainly be explained by organ filling variation between BT insertions and applicator position (Chakraborty et al 2014, Rangarajan 2018. For fractionated BT delivery, investigations are still ongoing to determine the necessity and accuracy of deformable image registration (DIR) to estimate the delivered dose in comparison with the state-of-the-art direct dose addition (DDA) of the dose volume histogram (DVH) indexes (Noe et al 2011, Andersen et al 2013, Hayashi et al 2015, Jamema et al 2015, Kobayashi et al 2015, Teo et al 2015, van Heerden et al 2017a, 2017b, 2018.…”

Development and validation of a novel scoring system to predict the risk of uterine perforation during intracavitary brachytherapy for cervical cancer

“…Sub-optimal insertion of the tandem can result in sub-optimal dose to the tumor while simultaneously leading to increased dose to nearby organs-at-risk. A perforation rate of 1.75%–15% (average=8%) has been reported in applicator insertions worldwide [ 7 8 9 10 ]. Post-insertion computed tomography (CT) enables identification of applicator, its position, suboptimal insertions, and uterine perforation [ 7 ].…”