Deep Inspiration Breath Hold Provides Fewer Set-up Errors Compared with Free Breathing for Whole-Breast Radiation

Abstract

To compare the set-up errors between deep inspiration breath-hold (DIBH) and free breathing (FB) for breast cancer patients who were treated with whole breast irradiation (WBI). We retrospectively enrolled 30 breast cancer patients receiving breast conserving surgery (BCS) following WBI using DIBH treated in our institution from April 2016 to June 2018 as study cohort. For the comparator, we identified 30 patients receiving WBI with FB. The kilovoltage cone-beam computed tomography (CBCT) was performed to evaluate and reduce set-up errors. The differences of set-up errors between techniques were compared using an independent two-sample t-test. The optimal margins from clinical target volume (CTV) to planning target volume (PTV) for DIBH were estimated. A total of 318 sets of CBCT images were acquired, with an average of 5.1±1.1sets per patient. The set-up errors along the three translational directions (lateral, longitudinal, vertical) were 2.1±1.6 mm, 2.6±1.7 mm, 2.5±2.1 mm for DIBH, and 2.2±1.7mm，3.1±2.5mm，3.3±2.3mm for FB group, respectively. Compared with FB, DIBH significantly reduced set-up errors in longitudinal (p=0.015) and vertical (p=0.004) directions. The optimal margins from CTV to PTV using DIBH were 6.2 mm, 7.3mm and 7.8 mm, respectively. In DIBH group, first week’s treatments and high body mass index (BMI) did not associate with larger set-up deviation. DIBH technique provides less set-up errors than free breathing for breast cancer patients treated with whole breast irradiation. The CTV- PTV margins of 6-8mm are recommended for DIBH.