Comparison of Deep Inspiration Breath Hold Left Breast Tangents With Active Breath Hold and Voluntary Breath Hold Using 3D Surface Image Guidance

Abstract

Deep inspiration breath hold (DIBH) may be used to reduce heart dose during radiation therapy for left breast cancer. This study compared two techniques of DIBH, active breath hold (ABH) and voluntary breath hold (VBH) using surface imaging guidance on their effectiveness and efficiency in DIBH treatment. Twenty patients, 10 in each technique, with early stage left breast cancer treated with tangent whole breast irradiation were retrospectively studied. VBH patients were the first ten treated using this technique while ABH had been used for a longer period of time. During CT simulation each patient underwent DIBH CTs, which were used to generate treatment plans. For reference purposes, free breathing (FB) simulation CTs were also acquired. Each patient had 3-6 weekly portal films through the course of treatment. We then retrospectively generated plans on FB CTs using the same dose criteria on PTVs Daily fraction dose for the whole breast was 180-200cGy for 18 patients and 266 cGy for 2 patients, one in each DIBH technique. Field in field was employed to increase dose uniformity. The left anterior descending (LAD) artery dose and the heart dose were evaluated. Heart position was evaluated on pretreatment verification films at breath hold. Treatment time was estimated as the difference of time stamps at initial set up and end of treatment, as recorded in record and verification system. Only days without portal films were analyzed. Both methods significantly reduced heart and LAD dose. The maximum LAD dose decreased by 89.6% ± 50.0% with ABH and 76.4% ± 55.5% with VBH. Decrease in mean heart dose and V30Gy was 66.5% ± 34.0% and 180.0% ± 40.0%, respectively with ABH, and 53.1% ± 25.0% and 171.9% ± 48.6%, respectively with VBH. Orthogonal setup film review from VBH patients showed that heart position deviation is small for most patients. The average heart position displacement was 0.1 ± 2.0 mm (S-I), 1.4 ± 3.1 mm (R-L), and 0.3 ± 1.9 mm (A-P). Comparable data for ABH patients is under study. Portal verification films confirmed the heart was effectively excluded from the treatment fields for all patients in both techniques. The treatment time was shorter with ABH (8.3 ± 6.0 mins) than VBH (13.8 ± 4.0 mins). All VBH patients tolerated voluntary breath hold for the entire treatment course. 2 ABH patients were unable to tolerate breath hold and were replanned and treated with free breathing. Both DIBH techniques effectively spared the heart during irradiation, with comparable reduction in heart dose. The differences in treatment time between the two techniques may be due in part to therapist familiarity with the technique, and may not be clinically significant with continued experience.