Purpose: To determine the diagnostic efficacy of (11)C-choline PET/CT in patients with prostate cancer (PC) after radical prostatectomy who presented with increasing PSA levels during follow-up in spite of being on hormone treatment (HT), and therefore showing HT resistance.
Methods: We evaluated a large series of 157 consecutive PC patients previously treated by radical prostatectomy who presented with biochemical recurrence with increasing PSA levels in spite of ongoing HT (HT-resistant patients). At the time of (11)C-choline PET/CT, the mean value of trigger PSA level was 8.3 (range 0.2 - 60.6 ng/mL), the mean PSA doubling time (PSAdt) was 5.3 (range 0.4 - 35 months), and the mean PSA velocity (PSAvel) was 22.1 ng/mL/year (range 0.12 - 82 ng/mL/year). (11)C-Choline PET/CT was performed following a standard procedure at our centre to investigate increasing PSA levels, either as the first imaging procedure or in patients with negative conventional imaging. At the time of (11)C-choline PET/CT all patients were receiving HT (61 were receiving monotherapy and 96 multidrug therapy). PET-positive findings were validated by: (a) transrectal US-guided biopsy in patients with recurrence in the prostatic bed, (b) surgical pelvic lymphadenectomy, (c) other imaging modalities, including repeated (11)C-choline PET/CT, performed during a minimum follow-up of 12-months.
Results: (11)C-Choline PET/CT showed positive findings in 104 of the 157 patients (66 %). (11)C-choline PET/CT detected: a single lesion in 40 patients (7 in the prostate bed, 10 in lymph nodes, 22 in bone, 1 at another site); two lesions in 18 patients (7 in lymph nodes, 7 in bone, 4 in both lymph nodes and bone); three or four lesions in 7 patients (4 in lymph nodes, 2 in bone, 1 at another site); and more than four lesions in the remaining 39 patients (2 in the prostate bed, 12 in lymph nodes, 12 in bone, 11 in both lymph nodes and bone, 2 at other sites). In (11)C-choline PET-negative patients, the mean values of trigger PSA, PSAdt and PSAvel were 3.8 ng/mL (range 0.2-11.9 ng/mL) 7.0 months (range 1.21 - 35 months) and 5.8 ng/mL/year (range 0.12 - 30.1) respectively, while in (11)C-Choline-PET-positive patients they were 10.5 ng/mL (range 0.2 - 60.6), 4.4 months (range 0.4 - 19.7) and 15.9 ng/mL/year (range 0.5 - 82.0) respectively. The differences between PET-negative and PET-positive patients were statistically significant for all these parameters: trigger PSA, p < 0.01; PSAdt, p < 0.01; PSAvel, p = 0.03.
Conclusion: In our patient population, (11)C-choline PET/CT was able to detect relapsed disease in a large proportion of HT-resistant PC patients during HT. These data, obtained in a large series, suggest that HT withdrawal before performing a (11)C-choline PET/CT scan may not be necessary for the detection of recurrent disease if PSA levels are increasing and PSA kinetics are rapid.