Prospective study evaluating the relative sensitivity of 18F-NaF PET/CT for detecting skeletal metastases from renal cell carcinoma in comparison to multidetector CT and 99mTc-MDP bone scintigraphy, using an adaptive trial design

Abstract

Background: The detection of occult bone metastases is a key factor in determining the management of patients with renal cell carcinoma (RCC), especially when curative surgery is considered. This prospective study assessed the sensitivity of 18F-labelled sodium fluoride in conjunction with Positron Emission Tomography/Computed Tomography (18F-NaF PET/CT) for detecting RCC bone metastases, compared to conventional imaging with bone scintigraphy or CT.

Patients and methods: An adaptive 2-stage trial design was utilized, which was stopped after the first stage due to statistical efficacy. Ten patients with Stage IV RCC and bone metastases were imaged with 18F-NaF PET/CT and 99mTc-labelled methylene diphosphonate (99mTc-MDP) bone scintigraphy including pelvic Single Photon Emission Computed Tomography (SPECT). Images were reported independently by experienced radiologists and nuclear medicine physicians using a 5-point scoring system.

Results: 77 lesions were diagnosed as malignant: 100% were identified by 18F-NaF PET/CT, 46% by CT and 29% by bone scintigraphy/SPECT. Standard-of-care imaging with CT and bone scintigraphy identified 65% of the metastases reported by 18F-NaF PET/CT. On an individual patient basis, 18F-NaF PET/CT detected more RCC metastases than 99mTc-MDP bone scintigraphy/SPECT or CT alone (p=0.007). The metabolic volumes, mean and maximum Standardized Uptake Values (SUVmean and SUVmax) of the malignant lesions were significantly greater than those of the benign lesions (p<0.001).

Conclusions: 18F-NaF PET/CT is significantly more sensitive at detecting RCC skeletal metastases than conventional bone scintigraphy or CT. The detection of occult bone metastases could greatly alter patient management, particularly in the context when standard-of-care imaging is negative for skeletal metastases.