Abstract
Brachytherapy is an important technique to increase the overall survival of cervical cancer patients. However, a possible shift of the applicators in relation to the target and organs at risk may occur between imaging and treatment. Without daily adaptive brachytherapy planning, these applicator displacements can lead to a significant change in dose distribution. In order to resolve it, a robust optimization method had been developed using a genetic algorithm combined with a median absolute deviation as a robustness evaluation function. The resulting robustness plans from our strategy might be worth considering according to the GEC-ESTRO guidelines. From the point of view of dose delivery uncertainty from applicator displacement, the robust optimization may be considered with caution in a single-plan approach for High Dose Rate brachytherapy treatment planning and should be confirmed by a more thorough investigation.
Highlights
Featured Application: This study developed a robust optimization algorithm to minimize dose delivery uncertainties by potential applicator-positional errors for magnetic resonance imaging (MRI) or computed tomography (CT)-based planning in the Cervix Brachytherapy
Planning data from five patients who had previously been treated with external beam radiotherapy (EBRT) followed by cervical High Dose Rate (HDR) brachytherapy with a Tandem-and-Ring (TR) applicator set was used as a representative sample in this retrospective study
To incorporate dose delivery uncertainty by potential applicator displacements, the translation of the applicator displacement set up 1 mm steps in the upper and lower bound of 5 mm in the x, y and z directions based on assumptions in the pre-study reports: the MRI-based 3D treatment plan for each fraction using only one MRI treatment, interfractional tandem displacement between multiple insertions [26], interapplication variation of doses and spatial location of the organ at risk (OAR) [27] and several reports by other groups [20,21,22]
Summary
Featured Application: This study developed a robust optimization algorithm to minimize dose delivery uncertainties by potential applicator-positional errors for MRI or CT-based planning in the Cervix Brachytherapy. It is important to improve clinical outcomes to minimize the dose to the organ at risk (OAR) when covering the target. Brachytherapy is an important technique to increase the overall survival of cervical cancer patients. From the point of view of dose delivery uncertainty from applicator displacement, the robust optimization may be considered with caution in a single-plan approach for High Dose Rate brachytherapy treatment planning and should be confirmed by a more thorough investigation. Cervical cancer patients with initial stages (stages IB—IIA) who undergo appropriate treatment will develop a recurrence with a risk factor of 10–15% [3,4]. A remote after-loading platform, including radioactive sources, allows for a more precise configuration of the dose to the target and the optimization of dwell times [10]
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