Preliminary report of a single-channel applicator in high dose rate afterloading brachytherapy for cervical cancer

Abstract

The aim of this study was to evaluate whether a patented single-channel applicator, which was modified from the traditional tandem applicator and wrapped with an oval-shield alloy around the source channel, has the same clinical efficacy and safety as the standard Fletcher-type applicator in high dose rate (HDR) brachytherapy for carcinoma of the cervix. Between December 2011 and February 2017, 299 patients with pathologically confirmed International Federation of Gynecology and Obstetrics (2009) stage Ib2-IVa cervical cancer were recruited to the trial and finished the allocated intervention. Of the first 151 patients, 71 were allocated to the Fletcher group and 80 to the single-channel group, satisfying the criteria for a preliminary analysis. All but 3 patients were treated with concurrent cisplatin chemotherapy and external beam radiotherapy followed by HDR brachytherapy. The 2-year overall survival, progression-free survival, and locoregional failure-free survival was 80.3%, 77.5%, and 78.9%, respectively, for the Fletcher group, and 86.3%, 82.5%, and 83.8%, respectively, for the single-channel group. The seriousness of acute treatment-related toxicities was similar in the 2 groups. The cumulative rate of late rectal complications of grade 3-4 in the Fletcher group and the single-channel group was 2.8% and 2.5%, respectively. The cumulative rate of grade 3 bladder complications was 2.8% for the Fletcher group and 1.3% for the single-channel group. The preliminary results of our study show that the patented single-channel intracavitary applicator might be able to provide protection for the rectum and bladder and seems to have the same clinical efficacy as the standard Fletcher-type 3-channel applicator in HDR brachytherapy for carcinoma of the cervix. This trial was registered with the Chinese Clinical Trial Registry (registration no. ChiCTR-TRC-12002321).

Keywords: cervical carcinoma; clinical trial; concurrent chemoradiotherapy; high dose rate brachytherapy; radiotherapy.

Figure 1

Sectional relative dose distributions of the single‐channel intracavitary applicator, tested using Mapcheck. A prescribed dose of 70 cGy was delivered to point A following optimized planning with a 6 cm effective length and a 1 cm step size. The ratio of the time between each spot was 13.9%, 11.0%, 6.8%, 8.3%, 15.5%, 22.5%, and 22.0%, respectively. A, Diagram showing the lead thicknesses in the anteroposterior and lateral directions. B, Dose distributions in cross‐sectional view. C, Dose distributions in coronal view. D, Dose distributions in sagittal view

Figure 2

Structure of the intracavitary applicators. A, Fletcher applicator sets (left) and single‐channel applicator (right) that comprises an internally lead‐shielded region, surrounded with an outer tube for placement and special canular structure to reduce artifacts (middle). B, Inner tube with lead‐shielding from a vertical view. The front and back direction of the lead should be consistent with the direction of the urinary bladder and the rectum

Figure 3

Flow diagram of trial participants with carcinoma of the cervix treated with Fletcher or single‐channel applicators of high dose rate brachytherapy

Figure 4

Kaplan‐Meier estimates of survival curves of patients with carcinoma of the cervix treated with Fletcher or single‐channel applicators of high dose rate brachytherapy. A, Overall survival. B, Progression‐free survival. C, Locoregional failure‐free survival. There were no significant differences between the 2 treatment groups