SNMMI: Dual tracers could deliver effectiveness, convenience + savings

A hybrid imaging technique which combines PET/CT with two molecular imaging agents targeting different markers of disease has been shown to aid in the detection of tumors in complex cases of bone cancer, according to research presented at the annual meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI).

Andrei Iagaru, MD, a lead investigator in the study and assistant professor of nuclear medicine in the department of radiology at Stanford University in Stanford, Calif., told Health Imaging that the study was designed to investigate the effect of combining F-18 NaF and F-18 FDG imaging agents in a single PET/CT scan. Previous research has shown that NaF is effective at detecting bone metastases, but Iagaru and colleagues wanted to see if combining imaging agents brought a result greater than the sum of its parts.

“With NaF, you only look for bone metastases,” said Iagaru. “If you give the FDG as well, you look for lesions elsewhere in the body. FDG will pick up some of the bone lesions, but not all of them. You add NaF to the FDG to increase sensitivity to bone lesions.”

The researchers conducted a retrospective review of 59 patients with biopsy-proven cancers. All patients underwent three separate scans: NaF PET/CT, FDG PET/CT and combined NaF/FDG PET/CT. A direct comparison for detected bone metastases was then performed between the three PET/CT scans and CT alone.

Results showed the composite NaF and FDG PET/CT images led to the identification of more bone metastases than the other techniques. The sensitivity, specificity, positive predictive value and negative predictive value for the combined scan were 0.96, 0.90, 0.88 and 0.96, respectively. These values were slightly improved over the NaF PET/CT scan by itself, but showed substantial benefit over FDG PET/CT and CT alone. The sensitivity of FDG PET/CT for detecting bone metastases was 0.64, and 0.59 for CT alone.

Although the differences in bone lesion detection were modest between the NaF PET/CT and the combined NaF/FDG PET/CT, Iagaru stressed the ability of FDG to detect other lesions elsewhere in the body and noted that overall healthcare costs could be reduced if multiple imaging scans were consolidated. It also streamlines the process for the patient.

“For certain patients who require both scans, it’s more convenient to have it all done in one session instead of coming twice to the hospital,” said Iagaru.

An estimated 2,890 new cases of primary bone and joint cancer, along with 1,410 fatalities from the disease, are expected to occur this year in the U.S., according to the National Cancer Institute. Iargaru said the number of bone metastases is much larger and it's in treating these patients where he sees the greatest opportunities for healthcare cost savings using NaF/FDG combo.