Purpose: The Deep Inspiration Breath Hold (DIBH) technique is recommended for patients with left sided breast cancer to minimize heart dose. Monitoring an external surrogate and providing visual feedback improves stability and reproducibility of voluntary breath holds. The BRAVEHeart (Breast Radiotherapy Audio-Visual Enhancement for sparing the Heart) trial compares two monitoring systems: (1) optical monitoring of the chest surface with built-in visual feedback screen (Breathe Well, Opus Medical Pty Ltd, Sydney) (2) infrared tracking of a marker block placed on the abdomen (RGSC, Varian Medical Systems, Palo Alto) with in-house visual feedback screen. The primary hypothesis was that the chest surface monitoring will be more accurate than abdominal monitoring.
Methods: Patients were randomized to, and imaged and treated with, either the chest surface or abdominal block monitoring system. During treatment cine EPID images were acquired and processed post-treatment to extract chest wall position. Treatment accuracy was quantified using chest wall displacement during treatment relative to the planned position. The correlation between the motion traces of external surrogates and the internal chest wall was assessed.
Results: Data was collected for 26 patients comprising 388 fractions. In assessing treatment accuracy, both systems showed similar systematic error (Breathe Well 0.4mm; RGSC 0.4mm), standard deviation of the systematic error (Breathe Well 0.7mm, RGSC 0.7mm) and random error (Breathe Well 1.37mm, RGSC 1.49mm). The primary hypothesis was rejected. On the Breathe Well arm 1.23% of EPID frames showed chest wall position >5mm from the planned position, with 0.72% for the RGSC arm. The median correlation coefficient between external surrogate motion and internal chest wall displacement per breath hold was Breathe Well: 0.41 and RGSC: 0.04.
Conclusion: Chest surface and abdominal block monitoring systems enabled treatment delivery with equivalent accuracy. Internal chest wall motion showed stronger correlations with chest surface movement than abdominal block motion.
Funding Support, Disclosures, and Conflict of Interest: NHMRC Development Grant (APP1073772) and National Breast Cancer Foundation Pilot Study Grant (PS-17-055). ES, KM and PK are inventors on a patent filed for the Breathe Well technology. KM and PK are founders, shareholders and directors of Opus Medical Pty Ltd, a company advancing the Breathe Well audiovisual biofeedback device.
Breast, Megavoltage Imaging, Patient Movement
TH- RT Interfraction Motion Management: General (most aspects)