FAP and neoplasm: In the blocking study, the tumor uptake of 68Ga-DOTA-4P(FAPI)4 decreased significantly when the mice were injected with unlabeled FAPI-46 1 h after injection, suggesting that the high tumor uptake of 68Ga-DOTA-4P(FAPI)4 was primarily a factor of its excellent FAP-targeting ability in vivo.