HIGH DOSE-RATE (HDR) CONFORMAL INTERSTITIAL BRACHYTHERAPY FOR LOCALLY RECURRENT RECTAL CANCER

REAL-TIME COMPUTED TOMOGRAPHY (CT) FLUOROSCOPY GUIDANCE AND IMAGE-BASED TREATMENT PLANNING

Abstract

Purpose: The aim of the study is to develop high dose-rate (HDR) conformal interstitial brachytherapy by means of combined real-time computed tomography (CT) fluoroscopy guidance with CT-based treatment planning for locally recurrent rectal carcinoma.
Materials and methods: The procedures of brachytherapy needle insertion were guided with a helical CT scanner providing real-time fluoroscopy reconstruction. A video monitor placed adjacent to the CT gantry simultaneously allowed the operator to see the process of needle insertion. CT images were transferred by an on-line system to the treatment-planning computer which reconstructed the implant needles and organ contours. The doses in planning target volume were normalized and geometrically optimized. The patients received a dose of 5 Gy per fraction on a daily hyperfractionation schedule at a total dose of 30-50 Gy with or without external radiation therapy. Nine patients were treated for this procedure.
Results: Thirteen to 36 needles (average 19.1) were successfully placed at the planning target volume in each patient. The average time for CT fluoroscopy was 370.1 seconds in each procedure. No accident was occurred during needle insertion, but one patient developed fibular nerve palsy after needle removal but gradually recovered. The CT-based treatment planning was faster and more accurate than projection reconstruction with conventional radiograms. Analysis of a dose volume histogram demonstrated conformal dose distribution of the target, while avoiding dose to normal structures with this method.
Conclusion: Real-time CT fluoroscopy ensures safety and increases the accuracy of needle placement. Conformal high dose-rate (HDR) interstitial brachytherapy with CT-based treatment planning is an attractive method for locally recurrent rectal cancer.