Abstract

Comparison of the Dosimetric Parameters Obtained with Active Breathing Coordinator (ABC) vs. Free-Breathing (FB) in Radiotherapy for Left- Sided Breast Cancer and Effect of Body Mass Index

Objective: Radio-toxicity hazard in breast cancer patients becomes a large-scale concern, proportional to the epidemiological figures and the growing population of breast cancer survivors. The present study compared the dosimetric efficacy of Deep Inspiration Breath Hold (DIBH) using Active Breathing Coordinator (ABC) with Free-Breathing (FB) in left-sided breast cancer patients and explored patient-related factors associated with ABC efficacy. Methods: We reviewed the treatment plans for 17 women with left-sided breast cancer, who were treated with external beam radiotherapy using the ABC system, between 2018-2020. CT-simulation images were compared between the two treatment plans including FB and ABC-DIBH. The compared dose-volume parameters included Left Lung V20 (%), Left Lung V5 (%), mean and maximum left lung doses, Heart V25 (%) and Heart V5 (%), and heart mean and maximum lung doses. The effect of body mass index was assessed. Results: The mean (SD) age of the participants was 45.29 (10.14) years, 6 (35.3%) were overweight and 6 (35.3%) were obese. ABC-DIBH was associated with significant relative decrease in all heart parameters including mean (40.9%, p=0.001) and maximum (14.4%, p=0.015) doses, and V25 (68.9%, p<0.001) and V5 (46.4%, p<0.001). However, no significant difference between the two techniques was observed in any of the lung parameters, including left lung mean (p=0.185) and maximum (p=0484) doses, or Left Lung V20 (p=0.122) or V5 (p=0.797). Left Lung V20 (R²=0.28, B=0.43, p=0.029) and Both Lung 20 (R²=0.28, B=0.21, p=0.028) were linearly correlated with BMI under ABC-DIBH, but not FB. Conclusion: The incorporation of DIBH with the ABC system improved heart sparing, which would reduce the radiation-induced cardiac morbidity and mortality; while, on other hand, it may increase lung radio-toxicity in obese patients.

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