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Gastrointestinal (GI) Cancer

Gastrointestinal cancer (GI) occurs when certain cells within the gastrointestinal tract grow in an uncontrolled, abnormal, manner. (GI) cancers occur anywhere along the long twisting tube that includes the esophagus, stomach, small and large intestine (which includes the colon), rectum and anus. Along the GI or digestive tract are three organs—the liver, gallbladder and pancreas—that contribute to the digestive process that turns food into energy for the body.

Sample Scan

Gastrointestinal (GI) Cancer

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Coronal and transversal 18F-FLT PET (A), conventional CT (B), and 18F-FDG PET (C) views of patient with gastric cancer (arrow).

According to estimates from the American Cancer Society, more than 90,000 new cases of GI cancer will be diagnosed in the United States and more than 63,000 people will die from the disease in 2011. Colorectal cancer, which includes malignancies in the large intestine and rectum, is the fourth leading cause of cancer deaths among both men and women.

Molecular imaging has become an essential tool in the diagnosis, evaluation and treatment of patients with gastrointestinal cancers. Currently used technologies include positron emission tomography (PET) and combination PET and computed tomography (CT) to diagnose and monitor the treatment of:

  • esophageal cancer
  • gastric (stomach) cancer
  • small bowel tumors
  • pancreatic cancer
  • lymphomas in the gastrointestinal tract
  • colorectal cancer

What is PET?

PET involves the use of an imaging device (PET scanner) and a tiny amount of radiotracer that is injected into the patient’s bloodstream. A frequently used PET radiotracer is fluorodeoxyglucose (FDG), which the body treats like the simple sugar glucose. It usually takes between 30 and 60 minutes for the FDG distribution throughout the body to become fixed. A CT is also obtained on the same machine so the FDG and CT scans can be fused together and compared.

How is PET used for GI cancers?

  • Diagnose and stage: by determining the location of the cancer and where the cancer has spread in the body.
  • Plan treatment: by determining a site that is appropriate for biopsy and in research studies helping select the best therapy based on the unique biology of the cancer and of the patient.
  • Evaluate how the cancer responds to treatment.
  • Manage ongoing care: by early detection of the cancer coming back.

Advantages of PET

Esophageal, Pancreatic and Gastric (stomach) Cancers
PET-CT is able to identify where cancer has spread in the body.

Gastric Cancer
PET-CT studies are used to assess patient response to chemotherapy.

GI Lymphoma

PET-CT plays an important role in the diagnosing and treatment of lymphomas of the GI tract by helping physicians:

  • Tell the size of the cancer, how actively that cancer may be growing, and the stage.
  • Evaluate patient response to treatment for both Hodgkin’s and non-Hodgkin lymphoma.
  • Tell if the cancer is coming back.


On the Horizon

New data from ongoing research indicates that for:

Esophageal Cancer
PET-CT may be useful in evaluating patient response to treatment.

Gastric (stomach) Cancer
PET-CT may be able to predict a patient’s response to chemotherapy.

Small intestinal tumors 
PET-CT may help physicians:

  • distinguish benign from malignant tumors.
  • distinguish a low- from high-grade sarcoma.
  • determine where cancer has spread in the body.
  • monitor patient response to treatment.

Pancreatic cancer
PET-CT may be useful for following a patient’s response to treatment.

GI Lymphoma
PET-CT may be able to predict a patient’s response to treatment very soon after therapy has begun.


Download the fact sheet: Molecular Imaging and Gastrointestinal Cancers