Whole-body 18F-fluorocholine (FCH) PET/CT and MRI of the spine for monitoring patients with castration-resistant prostate cancer metastatic to bone: a pilot study.

INTRODUCTION

Several treatments are proposed for castration-resistant prostate cancer (CRPC) at the metastatic stage. Monitoring of response using serum prostate-specific antigen (PSA) levels (sPSA) can be insufficient at this stage. Imaging has been proposed, in particular, nuclear medicine functional imaging and MRI, since response of predominant bone metastases is hardly evaluable on CT. Our aim was to evaluate in patients with CRPC with bone metastases, before and after various treatment lines, the evolution of sPSA, whole-body 18F-fluorocholine (FCH) PET/CT and spine MRI (sMRI) that has been proposed for detection of imminent malignant spinal cord compression.

PATIENTS AND METHODS

We retrospectively gathered a pilot series of 10 patients with CRPC metastatic to bone who had 47 PSA assays, FCH PET/CT, and spine-MRI (sMRI) performed concomitantly as routine examinations, before the beginning and at the end of 37 therapeutic intervals (TIs). Blinded reading of FCH PET/CT and sMRI was performed to evaluate visually whether or not the disease has been progressing (new lesions, greater size, or greater uptake intensity of known lesions) between the initial and the final examination of each TI.

RESULTS

Visual interpretations limited to spine FCH (sFCH) PET/CT and sMRI were in accordance for 34 TIs (92%): 14 progressions and 20 nonprogressions. In 2 cases, sFCH did not detect lesions visible on sMRI: one epiduritis and one 6-mm lesion. In 1 case, MRI missed a lesion in the sacrum that was detected on sFCH. When whole-body FCH (wbFCH) PET/CT was taken into account, the agreement with sMRI was limited to 29 TIs (78%). The 8 discrepant cases were all wbFCH positive and sMRI negative, that is, a significantly higher frequency of positivity for wbFCH (P < 0.008). Serum PSA levels increased by more than 25% during 21 TIs, whereas no progression was visible in 8 TIs on sMRI and in 2 TIs on wbFCH. In 5 TIs, sPSA decreased by more than 50%, and progression was never detected on imaging.

CONCLUSION

In detecting progression in patients with CRPC metastatic to bone, results of spine imaging with sMRI and sFCH PET/CT were highly correlated, whereas wbFCH PET/CT showed significantly more progression statues comparing to sMRI alone related to the exploration of other parts of the skeleton and of soft tissue.