Could a Re-Emerging PET/CT Agent Enhance Detection of Bone Metastasis in Prostate and Breast Cancer Cases?

New research shows that 18F-NaF PET/CT had higher sensitivity, accuracy, and negative predictive value than 99mTc-MDP SPECT for bone metastases in patients deemed to be at high risk for prostate cancer or breast cancer.

Is it time to rethink the imaging agent of choice for diagnosing bone metastases in people with prostate cancer or breast cancer?

In recently reported findings from a multicenter, phase III trial, researchers found that 18F-sodium fluoride positron emission tomography/computed tomography (18F-NaF PET/CT) was more effective than plantar bone scintigraphy with technetium-99m methylene diphosphonate (99mTc-MDP) single photon emission CT (SPECT) in the detection of bone metastases in patients with high-risk prostate or breast cancer.

For the comparative study, published in the Lancet Oncology, researchers assessed the use of 18F-NaF PET/CT and 99mTc-MDP SPECT in 261 patients (204 patients with prostate cancer and 57 patients with breast cancer) at 10 hospitals in Canada. According to the study, all of the study participants had imaging with both agents and all images were initially interpreted by board-certified nuclear medicine physicians.

The researchers found that 18F-NaF PET/CT had an 84.3 percent accuracy rate for diagnosing bone metastases in comparison to a 77.4 percent rate for 99mTc-MDP SPECT. The study authors noted that 18F-NaF PET/CT had over a 15 percent higher sensitivity rate (78.9 percent) in comparison to 99mTc-MDP SPECT (63.3 percent).

99mTc-MDP has been considered as the method of choice for the evaluation of bone metastases in various cancers. Since the limited spatial resolution of plantar scintigraphy and SPECT affects the sensitivity of bone scintigraphy for the detection of bone metastases, transition to the higher resolution of PET-CT with the use of 18F-NaF for the detection of these metastases is appealing,” wrote Jean-Claude Tardif, M.D., the director of the Research Centre at the Montreal Heart Institute and professor of medicine at the University of Montreal, and colleagues.

The study findings also revealed a higher negative predictive value (85.4 percent) for 18F-NaF PET/CT in comparison to 99mTc-MDP SPECT (76.9 percent).

Subsequent post-hoc analyses continued to demonstrate that 18F-NaF PET/CT had superior accuracy, sensitivity and negative predictive value (NPV) in comparison to 99mTc-MDP SPECT for the detection of bone metastases in those with prostate cancer. For patients with breast cancer, Tardif and colleagues noted that 18F-NaF PET/CT and 99mTc-MDP SPECT had equivalent sensitivity and NPV but 18F-NaF PET/CT had superior accuracy, specificity, and positive predictive value.

In regard to study limitations, the authors said there was no direct comparison of PET-CT and SPECT-CT. While all participants in the study group were deemed to be at high risk for bone metastasis, Tardif and colleagues said the study cohort was heterogenous for the staging, grade and histology of the initial tumor, treatments received and hormone receptor status among those with breast cancer. The study authors added that future research should examine the cost-effectiveness of 18F-NaF PET/CT over bone scintigraphy with 99mTc-MDP SPECT.