Introduction
In this chapter, the approach to gastrointestinal tumors will be discussed. Here we limit
ourselves to colorectal cancer (CRC), stomach or gastric cancer, and GIST (gastrointestinal stromal
tumor) sarcoma. Chapter 8 expands on esophageal cancer. Pancreas, liver, and biliary tract
malignancies are discussed in Chapter 10.
Advances in diagnostic imaging technology have improved establishing the diagnosis, staging and
restaging of disease, and monitoring response to therapy. Various imaging modalities are available
for this purpose, including the anatomical, e.g., radiography, computed tomography (CT), sonography
(US), magnetic resonance imaging (MRI), and functional modalities such as molecular imaging,
radioimmuno- and receptor scintigraphy, and magnetic resonance spectroscopy.
Conventional diagnostic methods have limited accuracy in early detection of primary as well as
recurrent CRC and gastric carcinoma. Assessment of disease extent or tumor burden is necessary for
proper patient selection for surgery with curative intent, or stratification to chemotherapy and/or
radiation treatment for patients with advanced disease. Appropriate non-invasive staging plays a
pivotal role in patient management. Integrated modalities such as positron emission tomography/
computed tomography (PET/CT) have changed the current work-up of patients with cancer (1). Some
refer to these combined gantries as dual, multimodality or hybrid imaging systems.