Brachytherapy dose changes: comparing in-room and out-room image-guided brachytherapy. A randomized study

Introduction
Image-based brachytherapy, involving an image machine and a brachytherapy unit in the same room (in-room brachytherapy [IRBT]), limits patient movements; however, this technique may not be feasible in high workload centers. In this study, we compared changes in the dose and volume of organs at risk (OARs) with out-room brachytherapy (ORBT) technique, in which patients musted be transferred to a waiting room and then transferred back for brachytherapy delivery.

Material and methods
This was a randomized prospective study comparing changes in D2cc doses and volume of OARs during IRBT and ORBT. Patients underwent CT for treatment planning (CT1) installed in brachytherapy loading room, and another CT immediately before brachytherapy (CT2) during each fraction. While patients remained on CT table after CT1 during treatment planning and delivery in IRBT arm, they were transferred out to waiting room and back to CT table in ORBT arm. CT2 was analyzed with CT1 to evaluate any changes in volumes and doses.

Results
A total of 294 fractions of brachytherapy were considered. The findings indicated no significant differences in the mean D2cc changes (Gy) (CT2 minus CT1) to the bladder, rectum, and sigmoid between IRBT and ORBT (mean ±SD: –0.07 ±0.36 vs. –0.01 ±0.39, p = 0.1426; –0.15 ±0.32 vs. –0.14 ±0.29, p = 0.8898; –0.17 ±0.38 vs. –0.19 ±0.31, p = 0.5221, respectively). Moreover, significant correlations were observed between D2cc changes and volume changes to each of OARs, p < 0.001.

Conclusions
IRBT does not result in differences in dose changes between planning and pre-treatment imaging when compared with ORBT. Consequently, ORBT can be considered for routine practice in high workload centers. Correlations in volume change and dose change to OARs were also observed.