Comparative analysis of 18F-FDG and 18F-NaF PET/CT in detecting osseous metastases in breast cancer

337 Objectives Breast cancer frequently metastasize to osseous structures. Fewer studies have explored use of 18F-FDG and 18F-NaF PET/CT scan in same patient population. In this retrospective analysis, we have assessed 18F-FDG and 18F-NaF PET/CT imaging in detecting osseous metastases in patients with history of breast cancer presenting to our center. Methods All patients with history of infiltrating ductal carcinoma of the breast who underwent both FDG and NaF PET/CT imaging during the year 2011 were retrospectively identified from radiology database. Radiology reports were examined to assess for demographics, indication for PET/CT imaging i.e. staging or restaging (after or during treatment) and involvement of osseous structures consistent with metastases. Results A total of 38 patients underwent 39 sequential 18F-FDG and 18F-NaF PET/CT imaging studies during 2011. Mean age of the patients was 51 years (range 30-77). Both imaging studies were completed within a one-week period. 11 imaging studies were performed for staging prior to initiation of treatment, while 28 were performed for restaging in patients who had received prior treatment. Overall, FDG PET/CT was positive for osseous disease in 9 studies compared to 16 on NaF PET/CT. On further sub-analysis; in staging population - 3 FDG PET/CT were positive compared to 4 NaF PET/CT scans. In restaging population - 6 FDG PET/CT were positive compared to a total of 12 positive NaF PET/CT imaging studies. All patients with positive 18F-FDG PET/CT imaging had positive 18F-NaF imaging. However, the difference didn’t reach statistical significance (p = 0.98), likely due to a smaller sample size. Conclusions 18F-NaF PET/CT appears to detect more osseous metastasis in patients with breast cancer. However, this disparity is more pronounced in restaging population (completed or on treatment). This difference may be due to underlying difference in healing or mineralization process detected on 18F-NaF PET/CT versus metabolism on 18F-FDG PET/CT. Prognostic implications of these findings are under review