Customized high-dose-rate brachytherapy using MRI planning for vaginal rhabdomyosarcoma.

PURPOSE: To report the technical aspects of customized high-dose-rate brachytherapy for vaginal rhabdomyosarcoma using MRI- and CT-based planning in a 20-month-old girl.

METHODS AND MATERIALS: An impression of the vaginal cavity at the resection site was taken after adequate lubrication of the vagina with lidocaine jelly. The impression was processed in the dental laboratory to obtain an MRI-compatible device with three imbedded catheters 0.4 mm apart, assuring tumor coverage. An MRI- and CT-based simulation under anesthesia with the applicator in place were performed, and the images were registered for contouring and planning to deliver 40 Gy in 10 fractions daily. Dose to the ovaries was limited to a mean dose less than 4 Gy. Treatment was delivered daily under anesthesia with no acute complications.

RESULTS: Brachytherapy using a customized applicator has many advantages over prefabricated vaginal cylinders for young girls. It allows greater dose distribution conformality with the possibility of contralateral vaginal wall sparing and more reproducible daily positioning. MRI-based planning is mainly performed to facilitate delineation of the target volume and the ovaries, which are easily identified on MRI.

CONCLUSIONS: The customized applicator offers many advantages of which treatment reproducibility, inherent MRI compatibility, and excellent dose distribution conformality. Our brachytherapy technique using MRI and CT scan planning allows precise tumor and normal tissues delineation resulting in excellent tumor coverage and normal tissues sparing.