In the subpopulation of post-prostatectomy BCR patients with PSA levels between 0.2 ng/mL and <1 ng/mL, in 18F-PSMA there was an overall positivity rate of 79.4% (27/34) (p = 0.001) with oligo-metastatic disease in 35.3% (12/34) (p = 0.002). The gene discussed is KLK3; the disease is metastatic neoplasm.