Colorectal adenocarcinoma is a type of cancer which develops in the colon or rectum. The colon and rectum make up what is known as the large bowel, or large intestine, in the lower section of the digestive tract, with the rectum forming the last portion of the gut. Usually, a colorectal adenocarcinoma arises from a benign, or non-cancerous, polyp which transforms to become malignant, or cancerous. As polyps may not cause symptoms, it is important to detect and remove them using screening programs before any malignant change occurs. Rectum and colon cancers are generally treated surgically, but chemotherapy, radiotherapy and drug therapies may also be used.
In around two thirds of cases, colorectal adenocarcinomas are found inside the colon, with one third occurring in the rectum. They arise from glandular tissue, in the epithelium lining the wall of the intestine. The risk of acquiring rectum and colon cancers increases with age, and colorectal cancer affects both men and women equally. Factors associated with a greater chance of developing colorectal adenocarcinoma include having a relative with the disease, having previously had cancerous growths in the large bowel, having an existing inflammatory bowel disease such as Crohn's, or being overweight.
Colorectal adenocarcinoma symptoms can vary depending on which part of the bowel is affected. Cancers located in the left side of the colon may be discovered sooner due to symptoms of pain, bleeding from the rectum, altered bowel habits and possibly a blocked gut or detectable lump. On the right side of the colon, tumors may go undetected because signs such as anemia, weight loss and bleeding not visible to the naked eye may be less obvious. A large non-cancerous polyp can also give rise to changes in bowel habits, anemia and rectal bleeding.
Making a diagnosis of colorectal adenocarcinoma involves a procedure known as a colonoscopy, where a slender instrument with a viewing camera is passed up through the anus into the large bowel. Tools attached to the instrument take samples of any suspicious areas of tissue which can then be studied microscopically. If cancer is detected, the treatment plan will depend on how far it has progressed.
The management of colorectal adenocarcinoma in its early stages, when it has not spread, typically involves removing the tumor using traditional or keyhole surgery techniques. If the cancer has spread to invade part of the colon, a section may have to be cut out in an operation known as a colectomy. In advanced cancers which have spread throughout the body, surgery is used to remove intestinal blockages and provide symptomatic relief. Drug treatments, radiotherapy and chemotherapy may be used in the later stages of cancer to reduce tumor growth and improve symptoms.
