The results of our volumetric evaluations performed to test [68Ga]Ga-PSMA-617 tumour selectivity demonstrated that [68Ga]Ga-PSMA-617 accumulates in large parts of the tumour that extend beyond the [18F]FET-avid margins, suggesting that [68Ga]Ga-PSMA-617 targets a complementary biological process to [18F]FET, and it might be a useful diagnostic marker to delineate parts of the recurrent tumour that are neoangiogenic, but not extremely metabolically active yet. This evidence concerns the gene FOLH1 and neoplasm.