2337 - Single Institution Retrospective Study of Tolerance of Voluntary Deep Inspiration Breath Hold for Abdominal Radiotherapy

S. Lee¹, C. Zeng¹, J. Jeong¹, G. Tang¹, E. D. Yorke¹, W. Harris¹, V. M. Williams², C. H. Crane², and L. Santanam¹; ¹Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, ²Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): Deep inspiration breath hold (DIBH) is widely used for radiotherapy of abdominal cancers to minimize the motion of the target and organs at risk during imaging and treatment delivery. During treatment, however, many patients demonstrate difficulties in maintaining the breath-hold level that they achieved voluntarily at simulation. This study investigates patient specific factors and characteristics in the breathing trace at simulation that can predict intolerance to DIBH during treatment, thus providing insights for fine tuning motion management strategies to each patient’s capacity. Materials/

Methods: We retrospectively studied 86 patients who received radiotherapy between January and July 2022 for abdominal cancers at a single institution. DIBH was implemented using a real time infrared monitoring system that tracks the motion of a reflective marker on the anterior thoracic surface. Patients received coaching by a radiation therapist to achieve a reproducible DIBH within 3 mm anteroposterior (AP) motion. A reference trace was recorded at simulation showing the marker displacement during DIBH and the free-breathing portions before and after DIBH. The study endpoint was any changes relative to the reference trace that were necessary for treatment. This was detected from the DIBH traces acquired during treatment. Correlation tests were conducted between the endpoint and 4 metrics extracted from the trace at simulation (AP levels at DIBH and during the expiration phase of the free breathing portion of the trace, and the period and amplitude of the free breathing portion). Additionally, 3 clinical and demographic factors at baseline were analyzed (age, Karnofsky Performance Scale, patient preferred language).
Results: Thirty percent (26/86) of the patients required modification to the planned DIBH protocol, including 22 DIBH level change for at least 1 fraction and 4 re-simulation under free-breathing. There was no statistically significant association at 5% false discovery rate (FDR) between the 7 investigated factors and DIBH protocol modification. Marginally significant associations were found for the DIBH AP level at simulation (FDR = 0.06, odds ratio = 1.06/mm, 95% confidence interval: 1.01/mm – 1.12/mm) and non-English language as a preferred language (FDR = 0.15, odds ratio = 4.52, 95% confidence interval: 0.99 – 20.61).
Conclusion: Despite the lack of statistical significance, the patient specific factors that are most predictive of DIBH tolerance were DIBH AP level and patient non-English language preference, which was in line with our clinical experience. To enhance patient tolerance to DIBH, patients need to be coached to avoid overly deep inspiration. Moreover, language barrier can have a potential impact, which may be mitigated by visual coaching.