Preliminary experience with 11C-acetate and positron emission tomography (PET) in prostate cancer

BACKGROUND: Imaging of relapses and metastases in prostate cancer is an open field in nuclear medicine and radiological examinations.Traditional FDG (fluorodeoxyglucose) PET is poorly sensitive especially for local recurrence. Prostate normal cells undergo malignant transformation loosing their capability of citrate production:this alteration leads to an increased turnover of acetate.Aim of our study was to evaluate 11C-acetate as a potentially good marker for in vivo imaging. METHODS: We examined 33(mean age 66 years) patients with previous prostate cancer submitted to surgery (31) and brachitherapy (2).19 out of them were on anti-androgen therapy.PSA values ranged from 0.5 to 21.9 and Gleason scale was from 4 to 9.PET was performed by a CT/PET scanner starting acquisition 5 min after injection of 555 MBq of 11C-acetate. RESULTS: Reconstructed images (coronal, sagittal and axial planes) were examined by a nuclear physician and a radiologist trained,respectively, in PET and CT. CT/PET was positive for relapse in 19 cases where we found 11 local relapses,8 abdominal nodal sites of metastases (from one to five),5 bone metastatic lesions (spread in 2 patients),1 brain lesion. 14 examinations were completely negative for tumor relapse.In the positive cases PSA ranged from 3,93 to 21,9 but it was 1.0 in the patient with brain lesion. In negative patients PSA values were comprised from 0.5 to 1.78. Final diagnosis was assessed by surgery in 2 and by clinical and instrumental evaluations.In 2 patients with negative CT/PET,local tumor recurrence was proved by MRI (FN).All positive examinations had a final diagnosis of relapse. CONCLUSIONS: From our preliminary data, 11C-acetate is sensitive to detect prostate recurrence when PSA is increased even if we did not find a relevant correlation between the number of metastases and PSA values:the case presenting 21.9 had three sites of abdominal nodes and a patient whose PSA was 8.55 showed spread bone and nodal metastases. PSA values seems not useful to decide proper treatment.Even if further data are needed,11C-acetate may be a better marker to assess the extension of disease and CT/PET is a worthful mean,for surgical purpose too,to localize the sites of relapse.