What are the causes and risk factors of GI cancer?

Causes for GI cancer. There are some genetic predispositions to them. Small intestine tumors are rare and probably missed. Colon cancer is associated to a low fiber diet, associated to colon polyps and more common in the industrialized word. Gastric cancer is more common in volcanic regions :japan, iceland, chile, c.R., smoked food intake ( nitrites) and were refrigeration of food is not adequate, and h. Pylori present.
Multiple. Stomach cancer: h. Pylori infection (kind of bacteria), alcohol, smoking, rare genetic syndromes. Pancreas: smoking, alcohol, genetic predisposition. Small bowel: none clearly established. Colon & rectum: family history. Anal: genital herpes, receptive anal intercourse, HIV positive.