High-risk cancer patients may be better managed with combined imaging modalities

PET/CT performed after the administration of both F-18 sodium fluoride (NaF) and F-18 fluorodeoxyglucose (FDG) beats both whole-body MRI and bone scintigraphy on accuracy in evaluating metastasis to bones from advanced breast and prostate cancers, according to a preliminary study running in the December issue of The Journal of Nuclear Medicine.

The same study, led by Ryogo Minamimoto, MD, of Stanford University, found that the radiopharmaceutical combo with PET/CT is as good as a combination of whole-body MRI and bone scintigraphy in evaluating patients at high risk of skeletal metastases—and so may serve as a “one-stop shop” in the imaging management of these patients.

The research team compared the imaging techniques as applied to 30 patients (15 women with breast cancer and 15 men with prostate cancer) who were referred for standard-of-care 99m Tc-MDP bone scintigraphy and prospectively enrolled in the study. 

Following the scintigraphy exam, all participants were scanned with NaF/FDG PET/CT and whole-body MRI using both unenhanced and contrast-enhanced sequences.

The team tabulated and compared skeletal as well as extraskeletal lesions detected with each test.

They reported that, for the detection of skeletal lesions, NaF/FDG PET/CT showed significantly higher sensitivity and accuracy than whole-body MRI (96.2 percent vs. 81.4 percent) and bone scintigraphy (96.2 percent vs. 64.6 percent) for the detection of skeletal lesions.

Also:

• Overall, NaF/FDG PET/CT showed higher sensitivity and accuracy than whole-body MRI (95.7 percent vs. 83.3 percent) but not statistically significantly so when compared with a combination of whole-body MRI and bone scintigraphy (95.7 percent vs. 91.6 percent).
• For extraskeletal lesions, NaF/FDG PET/CT and whole-body MRI had no statistically significant differences in sensitivity (92.9 percent vs. 92.9 percent), positive predictive value (81.3 percent vs. 86.7 percent) or accuracy (76.5 percent vs. 82.4 percent).
• NaF/FDG PET/CT showed no significant difference from a combination of NaF/FDG PET/ CT and whole-body MRI.

The researchers noted no statistically significant differences in positive predictive value among the exams.

In their study discussion, Minamimoto et al. conclude that NaF/FDG PET/CT is superior to whole-body MRI and 99m Tc-MDP scintigraphy for evaluation of skeletal disease extent, adding that proof of the option’s usefulness “may change the management of these patients.”

They also state that studies drawing from larger cohorts are needed to confirm their preliminary findings, “ideally using the newly introduced simultaneous PET/MRI scanners.”

In prepared remarks, corresponding study author Andrei Iagaru, MD, co-chief of Stanford’s Division of Nuclear Medicine and Molecular Imaging and co-director of its PET-MRI research program, says that, thanks to its low cost and reliable performance, bone scintigraphy will continue to be used as the initial tool for detecting skeletal metastases.

However, “evaluation of patients with negative/equivocal bone scans and high clinical suspicion for metastases will be done using combined modalities that may simplify the diagnostic algorithm for referring physicians and patients.”

Iagaru further states that the radiopharmaceutical PET/CT combo can guide the staging of patients with breast cancer higher than stage III and those with prostate cancer higher than stage II or PSA higher than 10, while whole-body MRI may remain worthwhile for detecting brain and liver metastases.

“More work remains to be done,” Iagaru says, “and our group is now exploring the use of combined NaF/FDG injections with state-of-the-art PET/MRI technology for significant decreases in radiation exposure and improved diagnostic performance in accurately evaluating extent of disease in cancer patients.”