[68Ga]Ga-PSMA-11 PET-CT: Local preliminary experience in prostate cancer biochemical recurrence patients.

Objectives: Clinical approach of prostate cancer (PCa) biochemical recurrence (BCR) is an ever-changing topic. Prostate-specific membrane antigen positron emission tomography ([68Ga]Ga-PSMA-11 PET-CTPSMA PET-CT) has shown good potential in this field. The aim is to evaluate PSMA PET-CT detection rate in PCa BCR and assess its impact on clinical outcome.

Material And Methods: Out of 319 patients with PCa who underwent PSMA PET-CT between October 2015 and June 2019, 70 had developed BCR after treatment with curative intent. Two groups were created: one with BCR after surgery (RP group) (N: 48; 68.6%) and other with BCR after radiotherapy (RT group) (N: 22; 31.4%). Clinical, analytical, pathological and PSMA PET-CT results were evaluated.

Results: Initial age was different between groups (p = 0.008). RP patients were mainly at intermediate risk (85.1% vs 42.9%, p = 0.001) while RT patients were at low risk of recurrence (8.5% vs 47.6%, p = 0.001). In RP and RT groups, PSMA PETCT detected, respectively, pelvic relapse in 31.3% and 63.6%, and extrapelvic relapse in 18.8% and 31.8%. Salvage treatment was performed in 61.9% (n = 26) of RP patients and in 15% (n = 3) of RT patients, p < 0.001. Of RP patients submitted to salvage treatment, 59.1% achieved complete remission. Concerning these patients, local radiotherapy led to complete remission in 68.4% (n = 13). Of RT patients submitted to salvage treatment, two had complete remission and one had partial remission.Concerning detection rate, PSMA PET-CT was positive for pelvic relapse when pre-PET PSA ≥ 0.8 ng/mL (RP) or ≥ 2.3 ng/mL (RT) and for extrapelvic relapse when PSA ≥ 0.4 ng/mL (RP) or ≥ 3.5 ng/mL (RT), p > 0.05.

Conclusions: Biochemical persistence rate after salvage therapy was similar (30-40%). The cut-off PSA values for pelvic relapse detected on PSMA PET-CT were ≥ 0.8 ng/mL (RP) and ≥ 2.3 ng/mL (RT).