What does this procedure involve?

High-Dose-Rate Brachytherapy (HDR-BT) combined with Intensity-Modulated Radiation Therapy (IMRT) is a two-part radiation treatment. First, IMRT delivers precisely shaped external beams to the tumor from multiple angles, minimizing damage to surrounding healthy tissue. Then, HDR-BT involves temporarily placing a small radioactive source directly into or near the tumor via catheters, delivering a high radiation dose in a few minutes. This is typically performed concurrently with chemotherapy over a 6- to 8-week outpatient schedule.