Dosimetric effects of the Smit sleeve on high-dose-rate brachytherapy tandem and ovoids plans for patients with locally advanced cervical cancer

Abstract

Purpose: Smit sleeves are used to facilitate insertion of the intrauterine tandem during brachytherapy for cervical cancer. When a tandem and ovoids system is used the base of the Smit sleeve displaces the ovoids distally. The dosimetric impact of this displacement is not known. Herein we performed a dosimetric analysis to quantify this impact on the integral dose and dose delivered to the organs at risk (OARs). Material and methods: Eleven high-dose-rate brachytherapy plans in which a Smit sleeve was used with a tandem and ovoids were reviewed. A second set of plans was generated modifying the position of the ovoids to simulate absence of the Smit sleeve. The high-risk clinical tumor volume (HR-CTV) dose coverage was maintained the same for both sets of plans by appropriately rescaling the dwell times of the simulated plan. The mean integral dose, D 2cc to the OARs (bladder, bowel, sigmoid and rectum) and the ICRU rectum point dose were compared between the original and modified plans using a paired two-sample t-test. Results: Simulating removal of the Smit sleeve was associated with an average reduction in the mean integral dose of 6.1% (p < 0.001) and an average reduction of 10.9% (p = 0.004) to the rectal D 2cc. Doses to the remaining OARs decreased to a lesser magnitude with only that of the sigmoid being statistically significant. Conclusions: The use of a Smit sleeve with a tandem and ovoids system could lead to the delivery of a higher mean integral dose to achieve similar HR-CTV coverage. In addition, it could increase the dose to surrounding OARs, primarily the rectum. The clinical significance of these findings is unknown, but the potential dosimetric impact of using a Smit sleeve should be taken into consideration during the planning when this device is used.

Prevention of uterine perforation during intracavitary brachytherapy of cervical cancer

“…reported that the Smit sleeve does have a dosimetric impact, which should be considered when a tandem and ovoids system is used. However, the use of a Smit sleeve with a tandem and ring applicators system does not have the same consequence on the applicators’ geometry [ 18 ].…”

Advantages of real-time transabdominal ultrasound guidance in combined interstitial/intracavitary cervical brachytherapy: a case-based review

“…To reduce this risk as well as improve confidence that distal needle position is within the target, our institution implemented transabdominal ultrasound (TA-US) guidance for tandem and needle placement in 2018. An added benefit from TA-US was the ability to perform treatments without the requirement for endocervical sleeves, which are prone to falling out during the course of treatment and may have unintended dosimetric effects [ 6 , 7 ]. In this pictorial essay, we provided a summary of the TA-US technique, presented clinical scenarios outlining the merits of real-time ultrasound guidance for IC/IS cervical brachytherapy, and reviewed dosimetric outcomes in the initial ten IC/IS brachytherapy patients treated at our center.…”