Purpose: An elevated serum prostate-specific antigen (PSA) level cannot distinguish between local-regional recurrences and the presence of distant metastases after treatment with curative intent for prostate cancer. With the advent of salvage treatment such as cryotherapy, it has become important to localize the site of recurrence (local or distant). In this study, the potential of (11)C-choline positron emission tomography (PET) to identify site of recurrence was investigated in patients with rising PSA after external-beam radiotherapy (EBRT).
Methods and materials: Seventy patients with histologically proven prostate cancer treated with EBRT and showing biochemical recurrence as defined by American Society for Therapeutic Radiology and Oncology consensus statement and 10 patients without recurrence underwent a PET scan using 400 MBq (11)C-choline intravenously. Biopsy-proven histology from the site of suspicion, findings with other imaging modalities, clinical follow-up and/or response to adjuvant therapy were used as comparative references.
Results: None of the 10 patients without biochemical recurrence had a positive PET scan. Fifty-seven of 70 patients with biochemical recurrence (median PSA 9.1 ng/mL; mean PSA 12.3 ng/mL) showed an abnormal uptake pattern (sensitivity 81%). The site of recurrence was only local in 41 of 57 patients (mean PSA 11.1 ng/mL at scan), locoregionally and/or distant in 16 of 57 patients (mean PSA 17.7 ng/mL). Overall the positive predictive value and negative predictive value for (11)C-choline PET scan were 1.0 and 0.44 respectively. Accuracy was 84%.
Conclusions: (11)C-choline PET scan is a sensitive technique to identify the site of recurrence in patients with PSA relapse after EBRT for prostate cancer.