Gastrointestinal cancer refers to malignant conditions of the gastrointestinal tract (GI tract) and accessory organs of digestion, including the esophagus, stomach, biliary system, pancreas, small intestine, large intestine, rectum and anus. The symptoms relate to the organ affected and can include obstruction (leading to difficulty swallowing or defecating), abnormal bleeding or other associated problems. The diagnosis often requires endoscopy, followed by biopsy of suspicious tissue. The treatment depends on the location of the tumor, as well as the type of cancer cell and whether it has invaded other tissues or spread elsewhere. These factors also determine the prognosis. Overall, the GI tract and the accessory organs of digestion (pancreas, liver, gall bladder) are responsible for more cancers and more deaths from cancer than any other system in the body. There is significant geographic variation in the rates of different gastrointestinal cancers. Upper digestive tract Esophageal cancer Esophageal cancer is the sixth-most-common cancer in the world, and its incidence is increasing. Some three to five males are affected for each female. An "esophageal cancer belt", in which the incidence of esophageal squamous cell carcinoma (SCC) is more than a hundred times that of adjacent areas, extends from northeastern China through central Asia to northern Iran. Ethiopia also has a notably high incidence. There are two main types of esophageal cancer—adenocarcinoma and squamous cell carcinoma. Worldwide, the incidence of each type is about the same, but in developed countries like North America and Europe adenocarcinoma is the more common. Cancer of the esophagus is often detected late inasmuch as there are typically no early symptoms. Nevertheless, if the cancer is caught soon enough, patients can have a five-year survival rate of 90% or above. By the time esophageal cancer is usually detected, though, it might have spread beyond the esophageal wall, and the survival rate drops significantly. In China, the overall five-year survival rate for advanced esophageal cancer is about 20%, and in the United States it is about 15%. Stomach cancer Cancer of the stomach, also called gastric cancer, is the fourth-most-common type of cancer and the second-highest cause of cancer death globally. Eastern Asia (China, Japan, Korea, Mongolia) is a high-risk area for gastric cancer, and North America, Australia, New Zealand and western and northern Africa are areas with low risk. The most common type of gastric cancer is adenocarcinoma, which causes about 750,000 deaths each year. Important factors that