Carotid intima-medial thickness as a marker of radiation-induced carotid atherosclerosis.

PURPOSE

Arterial thickening is a precursor to atherosclerosis. Carotid intima-medial thickness (CIMT), a measure of arterial thickening, is a validated surrogate for prediction of cerebrovascular events. This study investigates CIMT as an early marker of radiation-induced carotid artery damage.

MATERIALS/METHODS: Head and neck cancer patients treated with radiotherapy (RT) (minimum dose of 50 Gy) to one side of the neck (unirradiated side as control) at least 2 years previously were included. CIMT was measured in 4 arterial segments: proximal, mid, distal common carotid artery (CCA), and bifurcation and were compared to corresponding unirradiated segments. CIMT measurements >75th percentile of a reference population were considered abnormal and at increased cerebrovascular risk.

RESULTS

50 patients (34 males) with a median age of 58 years (interquartile range (IQR) 50-62) were included. The mean maximum dose to the irradiated and unirradiated artery was 53 Gy (standard deviation (SD) 13 Gy) and 1.9 Gy (SD 3.7 Gy), respectively. Mean CIMT was significantly greater in irradiated versus unirradiated arteries: proximal CCA (0.76 mm ± 0.15 vs 0.68 mm ± 0.14 (p<0.0001), mid CCA (0.74 mm ± 0.2 vs 0.68 mm ± 0.16 (p=0.01), distal CCA (0.77 mm ± 0.2 vs 0.68 mm ± 0.15 (p=0.004), and bifurcation (0.85 mm ± 0.25 vs 0.72 mm ± 0.17 (p=0.001). For all arterial segments, a significantly greater number of CIMT measurements were abnormal on the irradiated side (proximal: p=0.004, mid: p=0.05, distal: p=0.005, bifurcation: p=0.03). There was no effect of time from RT, age, smoking status, surgery and chemotherapy on CIMT difference (irradiated-unirradiated) in all segments.

CONCLUSIONS

CIMT is increased after RT and may be a useful marker of radiation-induced carotid atherosclerosis. There appears to be no additional effect of other atherosclerotic risk factors on CIMT following RT.