Detection of recurrence in patients with PSA relapse after external beam radiotherapy using ¹¹C-choline PET

Purpose: An elevated serum 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 11C-choline PET to identify site of recurrence was investigated in patients with rising PSA after external beam radiotherapy (EBRT). Methods and Materials: 70 patients with histological proven prostate cancer treated with EBRT and showing biochemical recurrence as defined by ASTRO consensus statement and 10 patients without recurrence underwent a PET scan using 400 MBq 11C-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. 57/70 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/ 57 patients (mean PSA 11.1 ng/mL at scan), locoregionally and/ or distant in 16/57 patients (mean PSA 17.7 ng/mL). Overall the PPV and NPV for 11C-choline PET scan were 1.0 and 0.44 respectively. Accuracy was 84%. Conclusions: 11C-choline PET scan is a sensitive technique to identify the site of recurrence in patients with PSA relapse after EBRT for prostate cancer.