Initial clinical experience with moderate deep-inspiration breath hold using an active breathing control device in the treatment of patients with left-sided breast cancer using external beam radiation therapy

Introduction: We present our initial clinical experience using moderate deep-inspiration breath hold (mDIBH) with an active breathing control (ABC) device to reduce heart dose in the treatment of patients with early-stage, left-sided breast cancer using external beam radiation therapy (EBRT) limited to the whole breast. Methods and Materials: Between February and August 2002, 5 patients with Stages I/II left-sided breast cancer received EBRT limited to the whole breast using an ABC device. After standard virtual simulation, patients with >2% of the heart receiving >30 Gy in free breathing were selected. All patients underwent a training session with the ABC apparatus to determine their ability to comfortably maintain mDIBH at 75% of the maximum inspiration capacity. Three patients received 45 Gy to the whole breast in 25 fractions, and 2 patients received 50.4 Gy in 28 fractions. For each of the medial and lateral tangential beams, radiation was delivered during 2 or 3 breath hold durations that ranged from 18 to 26 s. "Step-and-shoot" intensity modulation was employed to achieve uniform dose distribution. Open beam segments were purposely delivered over 2 breath hold sessions and captured on electronic portal images to allow intra- and interfraction setup error analysis. All electronic portal images of the tangential beams were analyzed off-line using an in-house treatment verification tool to assess the anteroposterior, craniocaudal, and rotational uncertainties. Corrections were applied if necessary. Results: A comparison of treatment plans performed on breath-hold and free-breathing CTs showed that ABC treatments achieved a mean absolute reduction of 3.6% in heart volume receiving 30 Gy (heart V₃₀) and 1.5% in the heart normal tissue complication probability. A total of 134 ABC treatment sessions were performed in the 5 patients. The average number of breath holds required per beam direction was 2.5 (4-6 per treatment) with a median duration of 22 s per breath hold (range: 10-26 s). Patients tolerated mDIBH well. The median treatment time was 18.2 min (range: 13-32 min), which was progressively shortened with increasing experience. A total of 509 portal images were analyzed. Combining measurements for all patients, the interfraction setup errors (1 SD) in the lateral and craniocaudal directions and in rotation were 2.4 mm, 3.2 mm, and 1°, respectively, for the medial beam and 2.3 mm, 3.1 mm, and 1°, respectively, for the lateral beam. For all patients, the intrafraction setup errors were about 1 mm and always less than 2 mm (1 SD). Conclusion: Reduction in heart V₃₀ can be achieved in patients with left-sided breast cancer using mDIBH assisted with an ABC device. With increasing experience, ABC treatments were streamlined and could be performed within a 15-min treatment slot. Our results suggest that mDIBH using an ABC device may provide one of the most promising methods of improving the efficacy of EBRT in patients with left-sided breast cancer, particularly when wide tangential beams are employed. Breast cancer; Breath hold; Radiation therapy; Intensity modulated radiation therapy.