Cardiac and Great Vessel Toxicity with Single Fraction Stereotactic Body Radiotherapy in Early-Stage Lung Cancer

Abstract

The relationship between thoracic radiotherapy and cardiovascular (CV) morbidity is an area of interest. When considering stereotactic body radiotherapy (SBRT) in the management of early-stage lung cancer, reports suggest CV dose may correlate with survival. To study this association for single fraction SBRT (SF-SBRT), we performed a retrospective review of patients treated at our institution assessing for associations between this dose schedule and CV toxicity. For the interval 2010-2022, we surveyed our IRB-approved prospective registry for SF-SBRT patients with tumors within 1 cm of the heart or any of the great vessels (GVs). Distance of the tumor to these structures was stratified as: directly contacting, within 0.5 cm, from 0.5-1 cm, or > 1 cm. Medical records were reviewed post-SBRT for CV events including: myocardial infarction (MI), heart failure (HF), structural heart damage (valvular or wall abnormalities), vascular damage (aneurysm, dilation, other abnormalities), hemoptysis, and arrhythmia which were correlated with lesion location and history. Four hundred four patients treated with SF-SBRT to 34 Gy in 1 fraction were identified. 35 patients (8.7%) had 36 lesions within 1 cm of the heart or GVs. 68.6% of patients were female and 74.3% were Caucasian. The median age was 72.5 years (range: 60-91), median Charlson comorbidity score was 6, median KPS was 80, and median ASCVD score was 21.0%. 33 patients had a smoking history with a median of 50 pack years. 12 patients (34.3%) had an arrhythmia prior to SBRT, 5 (14.2%) had prior HF, and 9 (25.7%) had prior MI or CV disease. All cases were non-small cell lung cancer or radiographic malignancy with 1 case of small cell lung cancer. Median tumor size was 1.6 cm. 91.4% of patients had stage I disease. Median follow-up was 2.26 years (0.37-4.0). Seven lesions (19.4%) were abutting the heart or GVs, 14 (38.9%) were within 0.5 cm, and 15 (41.7%) were from 0.5-1 cm. 54 events were observed with a median of 1 event per patient (0-5). The most common events were arrhythmia (15), vascular damage (9), structural damage (12), heart failure (9), and MI (6). The most commonly associated vascular structure was the aortic arch, while the most commonly involved substructures of the heart were the right atrium and left ventricle. 12 events occurred in the direct contact group, 17 in the < 0.5 cm group, and 25 in the 0.5-1 cm group. Patients with heart associated lesions accounted for 8 events, while those with vessel associated tumors accounted for 46. While cardiac events are relatively common in the medically inoperable SBRT population, they did not appear to be more common with tumors directly contacting major cardiovascular structures than for those with some separation. Most events could be attributed to medical causes other than SBRT. Further study is needed to clarify the potential role of radiation in events without direct explanation.