Safety and Accuracy of Employing Active Breathing Coordinator (ABC) Based Deep Inspiration Breath Hold (DIBH) Technique in Delivery of Radiation Therapy for Locally Advanced Left Sided Breast Cancer



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BACKGROUND: Patients with locally advanced breast cancer typically require complex field matching technique for radiation treatment delivery. While field matching has been demonstrated to be safe and effective in free breathing patients, its safety and accuracy in the setting of deep inspiration breath hold (DIBH) with active breathing coordinator technology (ABC) use has not been reported. OBJECTIVE: The purpose of this study is to determine the safety of ABC technology in DIBH of breast cancer patients requiring multi-field matching techniques. METHODS: 202 patients treated with DIBH/ABC technique at UT Southwestern between 2013-2018 were reviewed for this study. The amount of overlap or gap between the supraclavicular field and the chest wall field were measured and recorded for each treatment fraction prospectively to determine accuracy of setup. Optically stimulated luminescent dosimeter (OSLD) readings were taken at 1 cm above, below, and at the junction on at least 3 different fractions from 10 patients to determine accuracy of treatment dose. Acute and delayed skin toxicities, as defined by the common terminology criteria for adverse events v4.0, were collected and analyzed as a measure of treatment safety. RESULTS: 4973 fractions with gap/overlap measurements were analyzed. The average gap/overlap measured at junction was 0.28 mm+/-0.13 mm. 72% of fractions had a perfect match with 0 mm measurement, while 5.6% had an overlap and 22.7% had a measurable gap. Moreover, gap/overlap measurements neither improved nor worsened as patients received more treatment fractions. The median OSLD dose at 1 cm above the junction was 106%+/-7% of planned dose (range 94% to 116%); 1 cm below the junction, 114%+/-11% of planned dose (range 95% to 131%); at the junction, 106%+/-16.3% of planned dose (range 86% to 131%). These range of values appear to be within acceptable limits, since OSLD itself has a 10% calibration error, along with a likely minimal setup error. No significant acute or delayed skin toxicity at the matchline occurred in any patient. CONCLUSION: This work suggests that ABC assisted DIBH is a safe method of delivering radiation therapy in the setting of complex matching field technique for breast and regional nodal treatments.

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