MINIMAL RESPIRATORY MOTION OF THE BREAST IN FREE BREATHING: A 4D CT NARRATIVE VIDEO REVIEW.

Respiratory motion is a concern in radiotherapy of most sites, including breast cancer. Conventional radiation treatment planning routinely increases the margins around breast target volumes to account for motion. However, few studies have quantified the actual extent of respiratory motion during free breathing. A review of publicly available four-dimensional computed tomography (4D CT) video data was conducted to estimate the preponderance of breast respiratory motion. Selected videos were those containing sequences displaying movement of the breast/chest wall. Images were visually categorized as showing minimal motion if movements were estimated as ≤ 3 mm, moderate if about 5 mm, and substantial if about 10 mm or more. Respiratory motion of the breast/chest wall was minimal in 22 of the 38 cases (57.9%), moderate in 12 cases (31.6%), and substantial in 4 cases (10.5%). In line with emerging surface-guided data, this video review shows the frequent observation of minimal respiratory motion of the breast/chest wall. These findings question whether routine respiratory-motion-based target expansion is necessary in all patients.