Using 18F-FAPI PET to Detect Metastatic Disease in Patients That Have Gastric or Esophageal Cancer.

Inclusion Criteria:

* Male and female adults ≥ 18 years.
* Participants with confirmed gastric, esophageal or gastroesophageal malignancy undergoing staging evaluation for treatment planning.
* Eastern Cooperative Oncology Group (ECOG) performance status ≤2.
* Provided signed, written informed consent prior to any study-related procedures.
* Participants are required to have a ceCT scan of chest, abdomen and pelvis as per standard clinical practice and practice guidelines either 21 days or less prior to entry or planned within 21 days of \[¹⁸F\]FAPI-74 administration.
* For women who are not postmenopausal (two years of amenorrhea) or surgically sterile (absence of ovaries and/or uterus): agreement to use medically accepted, highly effective methods of contraception (e.g., hormonal implants, combined oral contraceptives, vasectomized partner, during the trial intervention period.

Exclusion Criteria:

* Unequivocal evidence of metastases at the time of enrollment that would preclude surgery as a treatment option.
* Known hypersensitivity to \[¹⁸F\]FAPI-74.
* Administration of another investigational diagnostic or therapeutic product within 30 days prior to \[¹⁸F\]FAPI-74 administration.
* Prior administration of a radiopharmaceutical within 10 half-lives of that product from the time of \[¹⁸F\]FAPI-74 administration.
* Previous cancer (except basal cell carcinoma of the skin or in situ carcinoma of the cervix/uterus (participants treated with curative intent and disease free for more than 5 years are permitted).
* Hepatic function: T. bili \>1.5X ULN or alk phos, ALT, or AST \>5X ULN
* Renal function: GFR \< 30 mL/min
* Pregnant or currently breast feeding (a negative pregnancy test is required in women of childbearing potential).
* Inability to undergo the PET/CT scanning procedure.
* Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
* Sarcoidosis
* Treatment, including chemotherapy, radiation, immunotherapy or surgery for curative intent of Gastroesophageal cancers