Diagnostic performance of ¹⁸F-choline PET-CT in prostate cancer

To evaluate the diagnostic performance of ¹⁸F-choline PETCT in staging prostate cancer (PC) and whether the use of this imaging modality changes the therapeutic decision in patients previously staged by conventional imaging. The secondary aim was to determine the prognostic factors associated with positive choline PETCT findings in both detection of disseminated disease and in changes in the therapeutic indication.

Multicentre, retrospective, observational study of 269 patients diagnosed with PC. Mean age was 69 ± 9.2 years. Of the 269 patients, 62 (23%) had high-risk localized PC (group 1), 118 (43.9%) biochemical failure after radical prostatectomy (group 2), and 89 (33.1%) biochemical failure after radiotherapy (group 3). None of the patients showed clear evidence of distant disease on computed tomography or bone scans. The following potential prognostic factors were assessed: PSA level at diagnosis; primary and secondary Gleason; Gleason score (GS); clinical and pathologic T and N stage; number of positive cylinders in the biopsy; presence of vascular or lymphatic invasion; status of surgical margins; androgen deprivation therapy (ADT); time to biochemical recurrence; and PSA, PSA doubling time (PSADT), and PSA velocity (PSAV) at failure. Univariate and multivariate analyses were performed, and receiver-operating curves calculated.

The mean PSA by groups was, group 1: 31.22 ng/ml, group 2: 2.52 ng/ml and group 3: 5.85 ng/ml. The tumor detection rate with ¹⁸F-choline PETCT was 74% (group 1: 85.5%, group 2: 55.1% and group 3: 91%). Prognostic factors for positive ¹⁸F-choline PETCT were identified only in group 2: PSA at failure and PSADT. ¹⁸F-choline PETCT changed the therapeutic indication in 62.8% (group 1: 71%, group 2: 55.2% and group 3: 70.1%). The prognostic factors for a change in treatment were identified only in group 1: secondary Gleason ≤ 4 and GS ≤ 7 and in group 2: PSA at failure, PSA nadir after surgery and pathologic stage N0. ¹⁸F-choline PETCT identified lymph node and/or metastatic disease in 32.7% (group 1: 25.8%, group 2: 29.7% and group 3: 41.6%). Prognostic factors for detecting lymph node/metastasis were identified in the group 2: PSA failure ≥ 1.37 ng/ml and PSADT < 4 months and in the group 3: PSADT < 4.6 months and time to failure < 5 years.

These findings support the clinical use de ¹⁸F-choline PET-CT in staging high-risk patients with a secondary Gleason ≤ 4 and GS ≤ 7, in restaging patients with biochemical recurrence after RP if PSA at failure ≥ 1.37 ng/ml or PSADT ≤ 4 months and in patients with biochemical failure after RT, if PSADT ≤ 4.6 months and time to failure < 5 years, because it determines a change in the therapeutic indication.