engleski

The most important clinical factors connected with the positive Ga-68-PSMA PET-CT scan in patients with biochemical recurrence of prostate cancer

Aim/Introduction: The aim of our study was to evaluate the diagnostic performance of 68Ga-PSMA PET-CT in patients with biochemical recurrence (BCR) of prostate cancer and to compare the results with PSA levels, PSAdt (doubling time), elapsed time from radical prostatectomy and Gleason score (GS). Materials and Methods: The study included 78 patients (median age 69y, range 49-84y ; median PSA value 0.47 ng/ml, PSA range 0.2-17, 4 ng/ml) who underwent 68Ga-PSMA PET-CT between April 2021 and March 2022. Results: 45 patients out of 78 (57.69%) were positive for active disease. In patients with PSA value of ≤0.5 ng/mL positivity rate (PR) was 53.49% (23/43), whereas patients with PSA > 0.5 ng/ml exhibited a PR of 65.71% (23/35). PSMA- PET/CT positivity in patients with a GS 7 was 50% (23/46), with GS 8 - 61.54% (8/13), and with GS 9 - 70% (7/10). Regarding PSAdt, out of 40 patients, PSMA-PET/CT PR was 66.67% (16/24) for PSAdt ≤6 months group, 64.29% (9/14) for PSAdt >6≤12 months, whereas in patients with PSAdt of >12 months only three patients were positive 25% (3/12). Out of all patients, androgen deprivation therapy (ADT) was reported in 25.64% (20/78) of the patients. 75% (15/20) of patients, that were ADT-treated, showed a positive Ga-PSMA PET-CT. In patients who were treated with only radical prostatectomy, positivity was correlated with shorter elapsed time from surgery. If a BCR of prostate cancer and PET/CT scan occurred within a year from surgery positivity was 92% (12/13). In the groups where PET-CT was performed more than a year after surgery positivity was significantly lower, only 35.3% (6/17). Local recurrence was found in 15.56%, lymph node metastases in 75.56%, and bone metastases in 28.89% of PSMA-PET/CT positive studies. Conclusion: 68Ga-PSMA PET/CT is a sensitive method for detection of lesions in early prostate cancer recurrence even in patients with very low PSA. Patients who were treated with radical prostatectomy only and had BCR and Ga-PSMA PET/CT scan within a year from surgery were almost all positive (92%), while the longer elapsed time from surgery was linked with a lower positivity rate (35.3%). We have shown that PSAdt may be considered the main positivity predictor of disease recurrence. Shorter PSAdt, even with low PSA was associated with a higher positivity rate, while longer PSAdt was most often linked with negative scans.

Ga-68-PSMA, prostate cancer, PET/CT, biochemical recurrence

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