JNM: FDG uptake may predict subsequent vascular events

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Increased FDG uptake in major arteries emerged as a strong predictor of a subsequent vascular event, according to a study in this month’s Journal of Nuclear Medicine.

With a cohort of nearly 1,000 asymptomatic patients with neoplastic disease, Axel Rominger, MD, from the department of nuclear medicine at the University of Munich in Germany, and colleagues sought to evaluate the association of arterial FDG uptake and calcifications in large arteries, as detected by PET/CT, with the subsequent occurrence of vascular events in otherwise asymptomatic cancer patients.

Researchers obtained clinical follow-up for 932 cancer patients examined with whole-body FDG-PET/CT (median follow-up, 29 months). Among this cohort, 279 patients had died from their oncologic disease.

In 1.6 percent of patients, a vascular event, defined as ischemic stroke, myocardial infarction or revascularization, was registered, according to the authors. The authors divided the maximum standardized uptake value by the blood-pool standardized uptake value, yielding a target-to-background ratio (TBR) for each arterial segment. They calculated the mean TBR as well as a calcified plaque sum score per patient in the major vessels: ascending, descending aorta, abdominal aorta and aortic arch, as well as iliac and carotid arteries.

Rominger and colleagues observed a significant correlation between mean TBR and calcified plaque sum. “Although calcified plaque sum significantly correlated with all conventional risk factors for vascular events, mean TBR correlated only with age, the male sex and hypertension,” they wrote.

The Cox regression hazard model identified a mean TBR of at least 1.7 and a calcified plaque sum of at least 15 as independent predictors for the occurrence of a vascular event, according to the authors. Patients with both mean TBR and calcified plaque sum above these thresholds were identified as having the highest risk for a future vascular event.

However, they found a mean TBR of at least 1.7 had greater prognostic value than did a calcified plaque sum of at least 15.

In addition to touting the effectiveness of the FDG uptake as a predictor, the authors concluded the concomitant severe vascular calcifications seemed to impart a particularly high risk.

The researchers also noted that FDG PET/CT is of proven reliability for detecting inflamed plaques in the walls of large arteries while also providing the means for counting calcified plaques. "These combined methods show excellent intra- and interreader reproducibility, as was confirmed by the present study,” they wrote.

However, Rominger and colleagues wrote that given the “small event rate in the present study, larger, prospective trials of patients without cancer are required to substantiate these promising results.”