Impact of (18)F-Fluoro-Methyl-Choline (FMC) PET/CT in the detection of recurrent prostate cancer: correlation with PSA kinetics and Radiological Imaging.

Objectives: We evaluated the potential role of (18)F­FMC PET/CT (PET) in the detection of recurrent disease or distant metastases in prostate cancer and biochemical evidence of recurrence and correlated its diagnostic accuracy with prostate­specific antigen (PSA) levels. Methods: from June 2015 to December 2016 we enrolled 118 selected patients with history of prostate cancer and PSA relapse. They underwent PET. At the time of PET, the mean PSA level was 2,2 + 0.7ng/mL and conventional imaging (ceCT, MR) were doubtful or negative for disease relapse. The final diagnosis of positive PET lesions was based on histopathology or in agreement with clinical findings or radiological imaging deepening. Results: PET was able to correctly detect malignant lesions in 73% (85/118) of patients but was negative in 27% (33/118). About patients with malignant lesions, 64.7% (55) had a local recurrence, 15.2% (13) a lymph nodes involvement and 12.9% (11) bone metastasis. The PET sensitivity was 77.5%, 80.7%, 85.2%, and 92.8% for the trigger PSA levels of more than 0.5, 1.0, 2.0, and 4.0 ng/mL, respectively. PET sensitivity was 33% in patients with a trigger PSA level of less than 0.3 ng/mL and 77% in patients with a trigger PSA level of greater than 0.3 ng/mL, respectively (P = 0.001). Sensitivity, Specificity, PPV and NPV of PET were respectively 87%, 90%, 92%, 86%. ceCT was positive in 38.9% (46/118) observing lymph nodes metastases in 13% (6), bone metastases in 21.7% (37) and local recurrence in 8.6% (4). Sensitivity Specificity PPV and NPV of ceCT were respectively 81%, 87%, 89%, 79%. MR was able to detect local recurrence of disease in 65 cases (55.8%) and pelvic lymph nodes involvement in 37 (31.3%) cases with a Sensitivity, Specificity, PPV and NPV respectively of 92%, 93%, 89%, 88%. 16 Patients (48.8%) with negative PET showed a PSA level from 0.12 to 14.3 ng/ml. Of the negative PET scans, 89% were observed in patients with PSA < 4 ng/ml and 87% in patients with a Gleason score <8. Conclusion: In patients with biochemical recurrence, PET shows its potential as a diagnostic modality unequal to correctly detect occult disease in 72% of patients and to discriminate local recurrence to systemic disease. Trigger PSA is a predictors of positive PET study. PET is not likely to have a significant impact on the care of prostate cancer patients with biochemical recurrence until PSA increases to above 4 ng/ml. Moreover PET seems to be better than ceCT for the staging disease in particular about distant metastases. MR seems to be better for the local recurrence updating and pelvic lymph nodes involvement.