Impact of patient transfer system on applicator stability and dosimetry in cervical cancer brachytherapy

Purpose:
This study aimed to evaluate applicator displacement due to patient transfer using traditional fixation (TRD) with and without patient transfer system (TS), and to assess its dosimetric impact on organs at risk (OARs).

Material and methods:
Computed tomography (CT) images, including high-risk clinical target volume (HR-CTV) and OARs structures, were analyzed from 46 treatment plans involving 32 patients undergoing intracavitary brachytherapy with tandem-ovoid applicator, using either traditional fixation (TRD) alone or in combination with patient transfer system (TRD + TS). Applicator displacement was assessed by measuring the distance between applicator base in two sets of CT images: one acquired during treatment planning (pre-plan), and second at dose delivery (pre-load). Dosimetric impact was evaluated for each simulated applicator shift.

Results:
The use of TRD + TS resulted in reduced applicator displacement compared with TRD alone. The mean magnitude of displacement decreased from 2.94 mm to 1.43 mm laterally, from 3.17 mm to 1.83 mm in the anterior-posterior direction, and from 3.45 mm to 2.00 mm longitudinally. Regarding dose variations to D_2cc for the bladder, rectum, sigmoid, and bowel, the average dose increases were 0.54%, 8.39%, 3.78%, and 0.58% for TRD, and 3.19%, 1.66%, 2.83%, and 1.19% for TRD + TS, respectively. No statistically significant difference was observed in either applicator displacement or radiation dose to OAR between the two systems.

Conclusions:
The combination of traditional fixation and patient transfer system have the potential to reduce applicator displacement, thereby enhancing treatment accuracy. However, in this study, no statistically significant difference was observed when compared with our traditional fixation method.