Diagnosing bone metastases. Pilot data from a prospective study comparing [99mTc]-MDP planar bone scintigraphy, whole body SPECT/CT, [18F]-fluoride PET/CT and [18F]-fluoride PET/MRI

Objectives [18F]-fluoride (NaF) PET/CT has gained widespread use in diagnosing bone metastases. The aim of this ongoing prospective study is to assess the diagnostic performance of NaF-PET/CT, planar bone scintigraphy (pBS) and whole-body SPECT/CT (SPECT/CT) for bone metastases in oncology patients.

Methods 120 patients with suspected bone metastases will be included. Patients undergo a pBS followed by SPECT/CT. Within 7 days a whole-body NaF-PET/CT followed immediately by NaF-PET/MRI is performed. pBS plus SPECT/CT and NaF-PET/CT are read separately by 1 NucMed (and 1 Rad). NaF-PET/MRI is read by a nuclear medicine specialist together with a MR-radiologist specialized in bone MRI.MRI served as reference standard in case of discrepancy between pBS, SPECT/CT and NaF-PET/CT. Primary analysis is performed on a per patient basis (bone metastases present or absent).

Results In 19 patients evaluated so far (Dec-2012), 6 patients had skeletal metastatic spread on MRI (32%). Sensitivity, specificity, PPV and NPV were: (pBS) 67%, 54%, 40%, and 78%, (SPECT/CT) 67%, 77%, 57%, and 83%, and (NaF PET/CT) 100%, 100%, 100% and 100%. In 8 patients there were discrepancies between the different modalities. In 6/8 patients this could be sorted out by PET/MR; 2/8 patients were rescanned with dedicated regional MRI.

Conclusions Pilot evaluation of pBS, SPECT/CT and NaF-PET/CT indicates that PET/CT is a highly sensitive and specific modality for detection of bone metastases. Additional information was provided by PET/MRI. Further head-to-head comparisons of PET/CT and PET/MRI and clinical follow-up will help in assessing a possible transition from standard pBS to NaF-PET based fusion imaging.