Clinical predictors of dosimetric precedence for (DIBH) radiation therapy for breast cancer
PO-1298
Abstract
Clinical predictors of dosimetric precedence for (DIBH) radiation therapy for breast cancer
Authors: Sania Abdelqader1, Fawzi Abuhijli2, Ramiz Abuhijlih2, Hanan Al-Masri2, Hiaitham Kana'an3, Anoud Alnsour4, Sara Mheid2, Issa Mohamad2, Hikmat Abdel-Razeq5
1king hussein cancer center, Radiation oncology, Amman , Jordan; 2king Hussein cancer center, Radiation oncology , Amman, Jordan; 3king Hussein cancer center, Radiation Oncology, Amman, Jordan; 4king Hussein cancer center, Radiation oncology , Amman , Jordan; 5king Hussein cancer center, Medical oncology , Amman, Jordan
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Purpose or Objective
We aim to evaluate the variables influence the effect of deep inspiration breath hold (DIBH) during left breast cancer radiation therapy (RT).
Material and Methods
Consecutive patients who underwent CT simulation for adjuvant left breast RT between 2019 and 2021, using a free breathing (FB) and DIBH techniques, were reviewed. For each patient, target and organs at risk volumes were contoured on both FB and DIBH scans, then RT plans were generated. RT was delivered as indicated to primary site with or without regional nodal irradiation using conventional tangential fields or VMAT techniques. Ipsilateral mean lung dose, percent of lung volume receiving >20 Grays (V20), mean heart dose, and percent of heart volume receiving >5 Grays (V5) were calculated in both techniques. Univariate and Multivariate analyses were performed to test the impact of radiation technique, nodal irradiation, patients’ age, smoking status, body mass index (BMI) and type of surgery on heart and lung dose reduction using the mean reduction values as cut off for comparison.
Results
Results A total of 90 patients were identified. Mean age was 44 years (range 23-69), mean BMI was 29.5 (range 22-40), 9 (10%) patients were planned using VMAT technique, 66 (73%) patients were non-smokers, 58 (64%) patients received radiation to chest wall, while 32 (36%) patients received radiation to breast and 73 (82%) patients received regional nodal irradiation. DIBH mean lung dose reduction ranged from 5%-47% (mean 18%), while heart dose reduction ranged 7%-70% (mean 39%) compared to FB. On univariate analysis, inclusion of regional nodal irradiation resulted in lower effectiveness in mean lung dose reduction (lung dose reduction less than 18% (p= 0.001)) the rest of variable did not significantly impact mean lung dose reduction. In regards to heart mean dose reduction; only high BMI significantly resulted in lower effectiveness in mean heart dose reduction (lower than 39%), which persisted on multivariate analysis (OR 0.843, [95% CI 0.76-0.934] (p= 0.0012)).
Conclusion
The use of DIBH reduces heart and ipsilateral mean lung dose for left sided adjuvant breast cancer RT. Patients’ BMI was inversely correlated with the dosimetric advantage of DIBH technique. Further studies are warranted to validate these results and dictate other factors that may influence DIBH value.