Rectal cancer--from genetics to the therapy.

Cancer of the colon and rectum is major cause of cancer-associated morbidity and mortality. Globally, it is the third most common cancer in males and fourth most common in females. Colorectal cancer is primarily a genetic disease with lesions being either somatically induced by environmental agents or inherited through the germline. Familial adenomatous polyposis and hereditary non-polyposis colorectal cancer are the main types of inherited colorectal cancer. Sporadic colorectal cancer is though to involve several genes in a multistep pathway. Colorectal cancer occurs as a result of a series of genetic alterations in normal tissue that lead to disorganization in the molecular mechanisms that control growth. Most of the evidence incriminating diets as a major factor in the genesis of colorectal cancer. Case control studies and complex statistical analyses implicate both causative and protective dietary factors. The aim of screening is to detect neoplasia of the colon and rectum before it reaches an advanced stage, survival being directly related to the stage at presentation. The most sensitive evaluation of the whole colon is by colonoscopy. The way forward continues to rest with research into more sensitive occult fecal blood tests, more cost-effective endoscopic protocols and greater knowledge of the biological factors triggering dysplastic changes in large bowel mucosa.