Pericoronary fat attenuation on coronary ct identifies persistent vascular inflammation after chest radiotherapy in cancer survivors

Background Cancer survivors remain at increased risk of coronary events even when obstructive coronary disease is mild. A key gap in routine care is detecting ongoing vascular inflammation, particularly after chest radiotherapy. Pericoronary adipose tissue attenuation on coronary computed tomography angiography (CCTA) is a practical imaging marker of coronary inflammation. Purpose To determine whether chest radiotherapy is associated with higher pericoronary fat attenuation on CCTA, and whether this inflammatory signal relates to high-risk plaque phenotype. Methods We retrospectively analyzed consecutive adults undergoing clinically indicated CCTA between 2021–2025. Cancer survivors were stratified into prior chest radiotherapy versus no radiotherapy and compared with age- and sex-matched non-cancer controls. Pericoronary fat attenuation was measured as mean attenuation (Hounsfield units) around the proximal right coronary artery. Coronary stenosis severity (CAD-RADS) and high-risk plaque features (low attenuation plaque, positive remodeling, spotty calcification, napkin-ring sign) were recorded. A subset with complete blood count within ±30 days was used to examine associations with neutrophil-to-lymphocyte ratio (NLR). Results A total of 318 patients were included (198 cancer survivors, 120 controls; mean age 53±11 years; 54% female). Among survivors, 76 (38%) had prior chest radiotherapy. Obstructive coronary disease was uncommon and comparable across groups (≥50% stenosis: 9% radiotherapy vs 7% no radiotherapy vs 8% controls; p=0.81). Pericoronary fat attenuation was higher (less negative) in radiotherapy survivors compared with non-radiotherapy survivors and controls (−69±7 vs −73±6 vs −75±6 HU; p<0.001). High-risk plaque features were more frequent in the radiotherapy group (21% vs 13% vs 10%; p=0.03). After adjustment for traditional risk factors, chest radiotherapy remained independently associated with higher pericoronary fat attenuation (β=+3.1 HU, p=0.002). In the CBC subset (n=210), higher NLR showed a modest association with higher pericoronary fat attenuation (r=0.24, p=0.01). Conclusion Chest radiotherapy is associated with a measurable CCTA inflammatory signature using pericoronary fat attenuation, even when stenosis severity is similar. This pragmatic CT-based marker may help identify cancer survivors with persistent vascular inflammation and higher plaque vulnerability, supporting more targeted preventive strategies.