Purpose: The aim of this prospective study was to compare the potential value of (18)F fluorocholine (FCH) and (18)F fluoride positron emission tomography (PET)-CT scanning for the detection of bony metastases from prostate cancer.
Methods: Thirty-eight men (mean age, 69+/-8 years) with biopsy-proven prostate cancer underwent both imaging modalities within a maximum interval of 2 weeks. Seventeen patients were evaluated preoperatively, and 21 patients were referred for post-operative evaluation of suspected recurrence or progression based on clinical algorithms. The number, sites and morphological patterns of bone lesions on (18)F FCH and (18)F fluoride PET-CT were correlated: Concordant lesions between the two modalities with corresponding changes on CT were considered to be positive for malignancy; discordant lesions were verified by follow-up examinations. The mean follow-up interval was 9.1 months.
Results: Overall, 321 lesions were evaluated in this study. In a lesion-based analysis, a relatively close agreement was found between these two imaging modalities for detection of malignant bone lesions (kappa=0.57), as well as in a patient-based analysis (kappa=0.76). Sixteen malignant sclerotic lesions with a high density were negative in both (18)F FCH and (18)F fluoride PET-CT [mean Hounsfield unit (HU), 1,148+/-364]. There was also a significant correlation between tracer intensity by SUV and density of sclerotic lesions by HU both in (18)F FCH PET-CT (r= -0.28, p < 0.006) and (18)F fluoride PET-CT (r= -0.20, p<0.05). The sensitivity, specificity and accuracy of PET-CT in the detection of bone metastases in prostate cancer was 81%, 93% and 86% for (18)F fluoride, and 74% (p=0.12), 99% (p=0.01) and 85% for FCH, respectively. (18)F FCH PET-CT led to a change in the management in two out of 38 patients due to the early detection of bone marrow metastases. (18)F fluoride PET-CT identified more lesions in some patients when compared with (18)F FCH PET-CT but did not change patient management.
Conclusion: FCH PET-CT may be superior for the early detection (i.e. bone marrow involvement) of metastatic bone disease. In patients with FCH-negative suspicious sclerotic lesions, a second bone-seeking agent (e.g. (18)F fluoride) is recommended. (18)F fluoride PET-CT demonstrated a higher sensitivity than (18)F FCH PET-CT, but the difference was not statistically significant. Furthermore, (18)F fluoride PET could be also negative in highly dense sclerotic lesions, which presumably reflects the effect of treatment. It will be important to clarify in future studies whether these lesions are clinically relevant when compared with metabolically active bone metastases.