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18F-choline positron emission tomography/computed tomography for the detection of prostate cancer relapse: assessment of maximum standardized uptake value correlation with prostate-specific antigen levels.

OBJECTIVE
Patients with prostate cancer are monitored by prostate-specific antigen (PSA) evaluation and PET [PET/computed tomography (CT)]. The aim of our study was to evaluate correlations between PSA levels and standardized uptake values (SUV) in patients with recurrent prostate cancer.


METHODS
We analyzed 282 prostate cancer patients undergoing PET-CT due to suspicion of recurrence. Levels of PSA and PSA change per month were analyzed, together with maximum standardized uptake value (SUVmax).


RESULTS
PET/CT results were positive in 175 patients (62.1%) and negative in 107 patients (37.9%). In the positive group, PSA levels were significantly higher. The ROC curve analysis indicated PSA level of 1.70 ng/ml and PSA level change in time of 0.12 ng/ml are the optimal cut-off values. Patients were divided into subgroups: with metastases (M), local relapse (L), and local relapse and metastases (M + L). The latest PSA levels, were similar in subgroups L and M: 5.00 (2.98-10.30) ng/ml and 3.90 (1.27-14.08) ng/ml, but lower than in subgroup M + L: 12.43 (6.08-49.36) ng/ml. PSA level change in time was similar in the subgroups L and M: 0.63 (0.09-1.00) ng/ml/month and 0.33 (0.02-1.73) ng/ml/month, but lower in subgroup M + L: 2.21 (0.22-10.34) ng/ml/month, P < 0.05. SUVmax was significantly (P < 0.05) lower in subgroup L than in M and L + M: 3.00 (2.30-4.00), 4.60 (2.70-7.40), and 4.90 (3.80-8.00), respectively. PSA level significantly correlated with SUVmax in patients from subgroups L (R = 0.424; P < 0.05) and M (R = 0.314; P < 0.01). Positive correlation between PSA change and SUVmax was observed in subgroup M + L (R = 0.561; P < 0.01) and M (R = 0.270; P < 0.05).


CONCLUSION
The study confirmed that patients with high PSA level and fast PSA increase are likely to be diagnosed with both, local relapse and metastases. Moreover, SUVmax values in metastatic lesions are usually higher.