Clinical usefulness of two-phase 18F-sodium-fluoride (18F-NaF) bone PET/CT for evaluating treatment response of bone metastases from breast cancer: Case report.

We report the case of a breast cancer patient in whom a two-phase ¹⁸F-sodium-fluoride (¹⁸F-NaF) bone PET/CT was useful for detecting hidden bone metastases and assessing treatment response. The patient underwent a two-phase bone PET/CT to evaluate a newly developed lesion found on bone scintigraphy following surgery. In the perfusion and bone phase PET/CT images, focally increased perfusion and bony uptake were found in the sacrum and L5 vertebra, suggesting bone metastases of breast cancer. Therefore, the patient subsequently underwent palliative treatment. In another twoPET/CT studies (each including two-phase bone images) performed after 3and 6months of follow-up, the perfusion phase images showed an improvement of the lesion uptake more clearly than in the bone phase images in the visual and semi-quantitative analyses, and thus the perfusion phase images were more useful for clarifying the treatment response earlier than the bone phase images. This is the first case showing the clinical usefulness of ¹⁸F-NaF bone PET/CT with the perfusion imaging technique for evaluating bone metastases and the therapeutic response of metastatic bone lesions.