Uptake of ¹⁸F-sodium fluoride (¹⁸F-NaF) can point to active vascular calcification associated with high-risk atherosclerotic plaque and may be a marker of high-risk abdominal aortic aneurysms (AAAs), according to a molecular imaging study.

Uptake of the biomarker on positron emission tomography (PET) and CT was significantly higher in the AAA (aortic diameter exceeding 40 mm) than in nonaneurysmal regions of the same aorta in the 20 patients studied. It was also significantly higher than in aortas of 20 controls in the prospective SoFIA³ study from researchers led by Rachael Forsythe, MD, of University of Edinburgh.

In a 72-person longitudinal cohort, the highest tertile of ¹⁸F-NaF uptake had aneurysms expand 3.10 mm per year versus 1.24 mm annually for the lowest tertile (P=0.008). The highest tertile also had triple the risk of AAA repair or rupture (15.3% versus 5.6%, log-rank P=0.043).

In this group with a baseline aneurysm diameter of 48.8 mm, 26.4% had their aneurysm repaired and 4.2% had a rupture and died without repair over 1.5 years of follow-up, Forsythe’s group reported in the Feb. 6 issue of the Journal of the American College of Cardiology.

“Fluorine-18-NaF PET-CT is a novel and promising approach to the identification of disease activity in patients with AAA and is an additive predictor of aneurysm growth and future clinical events,” the SoFIA³study authors concluded from their single-center, proof-of-concept study.

“This is the first study to demonstrate that an imaging biomarker of disease activity can add to the risk prediction of AAA and to suggest that this approach might refine clinical decisions regarding the need for surgery and improve patient outcomes,” they said. “We suggest that ¹⁸F-NaF uptake again relates to microcalcification and is particular to the most diseased areas associated with tissue disruption and loss of integrity.”

“Importantly, areas of fluoride uptake did not correspond to regions of macrocalcification on CT, suggesting the importance of dynamic calcification process,” noted an accompanying editorial.

In that commentary, Parmanand Singh, MD, of Weill Cornell Medical College, and Jagat Narula, MD, PhD, of Icahn School of Medicine at Mount Sinai, both in New York City, emphasized that “earlier detection of high-risk aneurysms is important to render appropriate care to the highest risk patients.”

“Despite significant advances in aortic imaging, pharmacotherapy and surgical interventions over the past decade, patients with AAA complications continue to have high rates of mortality,” they wrote. “The identification of aortic features linked to aortic vulnerability is crucial, both in guiding selection of patients for preemptive surgical repair and for optimizing timing of intervention to prevent complications. Noninvasive molecular imaging holds promise to identify markers of aortic instability earlier in the course of disease progression, and could offer a major advance in the diagnosis, surveillance and management of AAA.”