Lecture 16 development of colorectal cancer average age diagnosis is 72 colorectal cancer more likely to occur as people get older 3rd most common cancer and 2nd most common cause of cancer death most common malignancy in GI tract more than 90 people diagnosed over age 50 most common sites colon cancer spreads to directly through colorectal wall into nearby tissues through lymphatic system to nearby lymph nodes and through bloodstream to distant organs including the liver lungs bones brain ovaries deaths 49 7000 in 2015 due to colorectal cancer one of the most curable of gastrointestinal cancer industrialized nations appear to have the greatest risk while most developing nations have lower rates risk factors age over 50 colorectal polyps family history genetic alterations cigarette smoking diet personal history of cancer ulcerative colitis Crohn s disease polyps non cancerous growths that can become cancerous over time family history unless its treated an inherited condition called familial polyposis puts a person at very high risk age diet high in fat and low in fiber physical inactivity overview of carcinogenesis progression of colon cancer begins with the development of polyps in the epithelium of the colon Polyps are benign growths polyps get bigger nest of malignant cells may appear within the polyps if polyp isn t removed the malignant cells will metastasize at least 2 gene mutations involved 1 deletion of a healthy copy of the APC adenomatous polyposis coli tumor suppressor gene on chromosome 5 or p53 chromosome 17 2 A mutant proto oncogene often RAS symptoms change in bowel habits rectal bleeding or blood in stools persistent abdominal discomfort feeling that bowel doesn t empty completely weakness or fatigue unexplained weight loss screening is key to survival screening recommendations beginning at age 50 people at average risk undergo one of the following screening regiments fecal occult blood testing annually flexible sigmoidoscopy every 5 years double contrast barium enema every 5 10 years colonoscopy every 10 years colonoscopy most widely used diagnostic method to study the colon and has the highest diagnostic sensitivity and specificity of all available tests 90 95 of colon can be examined test usually takes an hour or less and may be both diagnostic and therapeutic offers flexibility of performing biopsy of suspicious regions and the ability of perform endoscopic polypectomy is preferred procedure of patients is the gold standard
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