Aim: F-18 fluor choline-positron emission tomography/computed tomography (FCH-PET/CT) has emerged as a new diagnostic tool for the imaging of prostate cancer. In this study, we have evaluated the potential role of FCH-PET/CT for the assessment of bone metastases in patients with prostate cancer. Furthermore, we assessed the pattern of metabolic uptake by FCH in relation to morphologic changes on CT.
Methods: Seventy men with biopsy-proven prostate cancer underwent FCH-PET/CT for preoperative staging or follow-up evaluation. Thirty-two patients were evaluated preoperatively, and 38 patients were referred for postoperative evaluation of suspected recurrence or progression based on clinical algorithms. PET imaging consisted of a dynamic PET/CT acquisition of the pelvic region during 8 min (1 min frames) starting 1 min after i.v. injection of 4.07 MBq/kg/bw FCH, which was followed immediately by a semi-whole body acquisition.
Results: Overall, 262 lesions showed increased uptake on FCH-PET. Two hundred ten lesions (210 of 262) were interpreted as bone metastases. The mean of maximum standardized uptake value (SUV(max)) in all malignant lesions was 8.1 +/- 3.9. Forty-nine lesions (24%) had no detectable morphological changes on CT-probably due to bone marrow metastases. Fifty-six sclerotic lesions (having a Hounsfield unit (HU) level of more than 825) were interpreted as highly suspicious for metastatic bone disease on CT and/or other imaging modalities such as the bone scan, but showed no FCH uptake. There was a significant correlation between tracer uptake as assessed by SUV and the density of sclerotic lesions by HU (r = -0.52, p < 0.001). The sensitivity, specificity, and accuracy of FCH-PET/CT in detecting bone metastases from prostate cancer was 79%, 97%, and 84%, respectively.
Conclusion: FCH-PET/CT showed promising results for the early detection of bone metastases in prostate cancer patients. We have found that a HU level of above 825 is associated with an absence of FCH uptake. Almost all of the FCH-negative sclerotic lesions were detected in patients who were under hormone therapy, which raises the possibility that these lesions might no longer be viable. However, clarification and the prognostic value of such lesions require further research.