Metronome-Assisted Shallow Breathing as a Motion Management Technique for Liver Tumor Stereotactic Body Radiotherapy

ABSTRACT

Treatment of primary and metastatic liver lesions with stereotactic body radiotherapy (SBRT) has made it essential to develop techniques to minimize target motion due to respiration. Common methods include inhibition with devices such as the Active Breathing Coordinator (ABC) system. However, the COVID-19 pandemic has made the use of some devices unfavorable given the theoretical risk of viral transmission. Another way to inhibit breathing motion is with faster, more shallow breathing. This retrospective study seeks to evaluate the effectiveness of a novel motion management technique using metronome-assisted shallow breathing (MASB). Consecutive patients treated between March, 2019 and July, 2021 for either primary or secondary liver tumors who were planned for SBRT and found to have ≥1cm motion on the 4DCT at the time of simulation. These patients then had a 4DCT with MASB with respiratory rates set between 24 and 29 breaths per minute via metronome guidance. To determine the effect of MASB on the radiation treatment volume we compared the average PTVs between MASB and FB groups using a paired t-test. To date, 17 of the 38 targets have been analyzed. Of the 17 targets, 9 targets (53%) had reduced PTVs with MASB 4DCT scans, the largest reduction was 19.6ccs. Of the 8 targets without decreased PTVs after MASB motion management, the largest difference was -8.89ccs. Overall, the average PTVs were smaller in the MASB group (58.32 ± 81.77) compared to the FB group (60.05 ± 85.22), a mean decrease of 1.74ccs (95% CI, -1.88 to 5.35), p-value = 0.32. Motion management with MASB did not show a statistically significant difference in PTV in this small sample, but will continue to serve as a useful technique for certain patients as it is easy and inexpensive to implement, provides higher 4DCT image quality, and offers a more comfortable experience compared to techniques such as ABC devices and abdominal compression. This is especially relevant in the era of COVID-19 when it is prudent to do the utmost to decrease the rate of viral transmission. Further analysis with a larger sample size is currently underway to determine which tumor location and patient population will most benefit from the MASB technique. [ FROM AUTHOR] Copyright of International Journal of Radiation Oncology, Biology, Physics is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)