Purpose: Radiotherapy for patients with large and pendulous breasts is often associated with higher lung and heart doses. One way to localize the pendulous breast away from the chest wall is to lift it into a tightly fitted bra. Surface detection-based localization is often utilized for real-time tracking for breast radiotherapy to ensure accurate treatment delivery. However, the breast and adjacent surface topography is manipulated by way of fitting the bra for large breast patients. This study is to investigate the accuracy and precision of Chabner XRT (CiVCO, Orange city, IA, USA) bra with AlignRT® (Vision RT, London, UK) surface tracking.
Methods: From 12/2020~2/2021, 58 breast patients received radiation treatment with surface tracking. Nineteen patients were treated with Chabner XRT bra and localized with AlignRT®. MV verification films were taken daily to compare with VisionRT surface tracking deltas in the patient SI, AP and LR directions.
Results: About 30% of breast patients utilized Chabner XRT bra during their radiation treatment in our intuition. 85% (16 out of 19) of these bra-fitted patients showed good surface tracking (within 1mm in all 3 directions) with AlignRT®. However, for smaller breast depths (differences between upper chest and bust circumferences, e.g., C cup) together with a relatively larger lower chest band (e.g. 40 inches), the breast tissue of these patients (3 out of 19) tends to equally distributed to their entire breast in the treatment position, resulting in a lower bra precision to reflect the breast surface. The bra surface could mislead the surface tracking. Because of this, these three patients required daily film verification
Conclusion: Bra with surface tracking is accurate and precise for normal breast sizes. When the patient has a small breast depth and larger lower chest band circumference, surface tracking could be compromised.