Dose to the Cardiac Substructures/Great Vessels and Survival in Patients Treated with Definitive Stereotactic Body Radiation Therapy for Lung Tumors – A Pilot Study

• Published in: International journal of radiation oncology, biology, physics Vol. 120; no. 2; p. e9
• Main Authors: Buchberger, D.S., Busch, C., Guo, B., Weragoda, S., Xia, P., Reddy, C.A., Stephans, K.L., Videtic, G.M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2024
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2024.07.1798

Stereotactic body radiation therapy (SBRT) is the standard of care for medically inoperable early-stage lung cancer. Recent reports suggest that doses to cardiovascular substructures may correlate with survival. We performed a retrospective analysis of our institutional lung SBRT patients to investigate potential associations. For the interval 2014-2023, we surveyed our IRB-approved prospective registry for lung tumors within 1 cm of the heart or great vessels (GV) treated definitively with SBRT. Using a commercial DL-based contouring platform, select substructures of the heart and GV were contoured. These included: right atrium, right ventricle, left atrium, left ventricle, inferior vena cava, superior vena cava, and aorta. Contours of the sinoatrial node and atrioventricular node were generated using an in-house workflow. Dosimetric analysis was performed to ascertain doses for each substructure. Parameters assessed included mean doses, maximum doses, and volumetric doses. Primary outcomes of interest were non-cancer related death (NCRD), all-cause mortality (ACM) and toxicity. Competing risk regression was used to identify factors associated with NCRD and Cox proportional hazards regression was used for ACM. 89 patients were identified. Median follow-up was 22 months. Median age was 74.8 years. 55.1% was female. Median KPS and age adjusted Charlson score were 80 and 7, respectively. Median tumor size and PET SUV max were 2.7 cm and 10.7. Comorbid conditions at SBRT were as follows: 14.6% cerebrovascular disease, 67.4% COPD, 18% CHF, 36% coronary artery disease, 20.2% diabetes, 9% elevated cholesterol, 66.3% hypertension, 11.2% myocardial infarct, 27% peripheral vascular disease. SBRT regimens were 50 Gy in 5 fractions (77.5%), 60 Gy in 5 fractions (9.0%), 60 Gy in 8 fractions (4.5%), and 34 Gy in 1 fraction (3.4%). For the cohort, 23.6% of the group experienced any grade toxicity. There were 6 reported cardiovascular toxicities (6.7%). There were no grade 5 cardiovascular toxicities; there were 2 grade 4 toxicities (2.2%; heart failure/persistent AF; new onset AF). The 1- and 2-year rates of NCRD were 11.2% (95% CI 5.7-18.8%) and 22.0% (95% CI 13.9-31.3%). The 1- and 2-year rates of ACM were 26.4% (95% CI 10.5-26.4%) and 48.5% (95% CI 28.0-45.8%). On multivariable analysis, KPS (HR 0.95, 95% CI 0.91-0.99) and the dose to 1 mL of the aorta (HR 1.04, 95% CI 1.01-1.07) were the only variables significantly associated with NCRD. Only KPS (HR 0.97, 95% CI 0.94-0.99) and tumor size (HR 1.28, 95% CI 1.06-1.55) were significantly associated with ACM on multivariable analysis. In this retrospective study, the dose to 1 mL of the aorta was significantly associated with NCRD in patients treated with definitive SBRT. Dose to other substructures of the heart and GV was not correlated with NCRD. Further study is needed for validation.