Stomach cancer CT

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Parminder Dhingra, M.D. [2]

Abdominal CT scan may be helpful in the diagnosis of stomach cancer. It is used to evaluate metastatic disease, especially hepatic or adnexal metastases, ascites, or distant nodal spread. Integrated PET/CT imaging can be useful to confirm malignant involvement of CT-detected lymphadenopathy. A negative PET CT is not helpful, since even large tumors with a diameter of several centimeters may not be visible on PET scan if the tumor cells have a fairly low metabolic activity.

• CT is procedure of choice used to assess the T stage (extent) of the primary tumor.^[1]
• It is used to evaluate metastatic disease, especially hepatic or adnexal metastases, ascites, or distant nodal spread.
• Peritoneal metastases and hematogenous metastases smaller than 5 mm are frequently missed by CT scan in 20 percent of patients.^[2]
• Sensitivity rates are from 65 to 97% and specificity rates for regional metastases 49 to 90%.^[3]

Demonstration of lesions facilitated by negative contrast agents:^[4]

• A polypoid mass with or without ulceration.
• Focal wall thickening with mucosal irregularity or focal infiltration of wall.
• Ulceration: gas-filled ulcer crater within mass.
• Infiltrating carcinoma: wall thickening and loss of normal rugal fold pattern.

• Integrated PET/CT imaging can be useful to confirm malignant involvement of CT-detected lymphadenopathy.^[5]
• It directly visualizes the liver surface, the peritoneum, and local lymph nodes.
• A negative PET CT is not helpful since even large tumors with a diameter of several centimeters may not be visible on PET-CT if the tumor cells have a fairly low metabolic activity. Signet ring carcinomas are not FDG avid.^[6]
• The main benefit of PET is that it is more sensitive than CT scanning for the detection of distant metastases.^[7]
• PET CT is not an adequate replacement for staging laparoscopy.^[8]

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