SU‐GG‐T‐150: Accelerated Partial Breast Robotic IMRT with CyberKnife: Case Study and Clinical Experience

Purpose: To report case‐study and experience of the first RoboticIntensity Modulated Radiation Therapy (RIMRT) for Accelerated Partial Breast Irradiation (APBI) using the CyberKnife® RoboticRadiosurgery System. Method and Materials: RIMRT with CyberKnife® for APBI has some unique advantages over conventional APBI. Brachytherapy techniques are invasive and can cause short term problems such as discomfort, wound care and risk of infection and bleeding. These risks are eliminated by highly accurate, non‐invasive CyberKnife procedure. Respiratory motion compensation and the sub‐millimeter targeting accuracy of CyberKnife eliminate target position uncertainty in the conventional 3‐D Conformai APBI, thereby reducing the need for expanded PTV. But CyberKnife procedures are challenging. Fiducial may migrate, making the target localization difficult. It may be challenging to reproduce treatment setup or fiducial localization due to patient setup or breast location with respect to the body contour. In this study we report our experience with the first RIMRT case with CyberKnife in our clinic. A set of five fiducials were inserted around the tumor. Two sets of CTimages were acquired one week apart to evaluate fiducial migration. Prior to treatment, patient underwent tracking simulation to assess fiducial visibility in live images and tracking and breathing model quality. Breast immobilization was avoided in order to assess reproducibility. Results: The patient received 47.5 Gy in 10 fractions. No fiducial migration was observed. Excellent fiducial image quality was observed throughout the treatment. No effect of breast location with respect to the body contour was observed on the image quality; the treatment setup was easily reproducible. Conclusion: In the 3‐month follow‐up, patient stated pleasure with the cosmesis and outcome of the RIMRT. 3‐month follow‐up MRI indicates decrease in size and change in enhancement characteristics of the lesion. RIMRT with CyberKnife promises to be a new, non‐invasive and highly accurate technique for APBI.