(68) Ga-PSMA has a high detection rate of prostate cancer recurrence outside the prostatic fossa in patients being considered for salvage radiation treatment

Objectives: To examine the detection rates of (68) Ga-PSMA-positron emission tomography (PET)/computed tomography (CT) in patients with biochemical recurrence (BCR) after radical prostatectomy (RP), and also the impact on their management.

Materials and methods: A total of 300 consecutive patients with prostate cancer (PCa) who underwent (68) Ga-PSMA-PET/CT between February and July 2015 were prospectively included in the Prostate Cancer Imaging (ProCan-I) database. For the present analysis, we included patients with BCR (prostate-specific antigen [PSA] level ≥0.05 and <1.0 ng/mL) after RP, who were being considered for salvage radiation therapy (RT) according to the Faculty of Radiation Oncology Genito-Urinary Group (FROGG) guidelines. Two readers assessed each (68) Ga-PSMA-PET/CT, and all positive lesions were assigned to an anatomical location. For each patient, the clinical and pathological features were recorded, their association with pathological (68) Ga-PSMA uptake was investigated, and detection rates were determined according to PSA level.

Results: A total of 70 patients were included, and 53 positive (68) Ga-PSMA lesions were detected in 38 (54%) patients. Among patients with PSA levels 0.05-0.09 ng/mL, 8% were definitely positive; the corresponding percentages for the other PSA ranges were as follows: PSA 0.1-0.19 ng/mL, 23%; PSA 0.2-0.29 ng/mL, 58%; PSA 0.3-0.49 ng/mL, 36%; and PSA 0.5-0.99 ng/mL, 57%. Eighteen of 70 patients (27%) had pathological (68) Ga-PSMA uptake in the prostatic fossa, 11 (14.3%) in the pelvic nodes, and five (4.3%) in both the fossa and pelvic lymph nodes. Finally, there was uptake outside the pelvis with or without a lesion in the fossa or pelvic lymph nodes in four cases (8.6%). As a result of the (68) Ga-PSMA findings there was a major management change in 20 (28.6%) patients.

Conclusions: (68) Ga-PSMA appears to be useful for re-staging of PCa in patients with rising PSA levels who are being considered for salvage RT even at PSA levels <0.5 ng/mL. These results underline the need for further prospective trials to evaluate the changes in RT volume or management attributable to (68) Ga-PSMA findings.