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Facts About Colorectal Cancers

Know what to look for when colorectal cancer is suspected.

Colorectal cancer is cancer arising from the inner lining of the large intestine. This includes the entire colon and the rectum which together form part of the gastrointestinal tract lying between the small intestine and the anus.

There is quite a lot of misunderstanding regarding the aetiology or causation of colorectal cancer. About 5% of all cases of colorectal cancer are due to a direct chromosomal abnormality which is inherited in an autosomal dominant fashion. This sort of condition includes familial polyposis coli or what is nowadays called familial adenomatous polyposis (a condition characterised by the presence of numerous internal polyps) or FAP and Peutz-Jeghers polyposis. In these conditions, 50% of family members who inherit the affected gene will manifest numerous polyps in the intestines.

In FAP, by the time of late teenage years, most of the affected members will have had intestinal cancers amongst the thousands of polyps in the large intestine. Therefore, preventive surgery before cancer develops is normally advised. Fifteen percent of all colorectal cancers have a multifactorial causation including genetic influences; these genetic factors may be stronger in some families than in other families. Families with multifactorial but strong genetic influences for colorectal cancer are called Hereditary Non-Polyposis Colorectal Cancer Syndrome (HNPCC). These families can either present with colorectal cancers alone or with female genital tract, urinary tract, stomach, breast and other sorts of cancers as well. The primary problem is genetic. And such families manifest colorectal and affected cancers at least 10 to 20 years younger than people without such a family history.

Unfortunately about 80% of all colorectal cancers either do not have or have only a non-significant family history. This means we should not ignore screening just because we do not a strong family history of colorectal cancer.


The colon and rectum is a conduit for the passage of faecal matter. In the right side of the colon the faecal contents are fluid and symptoms are only seen when the colonic lumen is almost completely blocked. The tumour therefore has to be very big before symptoms are seen. Left sided colonic cancers normally present when the cancers are smaller as the left colon is small in diameter and the contents are more solid.

Symptoms manifest in several ways. Firstly when the faeces scrapes against the tumour, there may be bleeding or the irritation may result in large amounts of mucus produced. Small amounts of bleeding over a long period of time (months) may result in symptoms of anaemia. Profuse bleeding is rare. Cancers in the left colon may cause obstruction with symptoms of abdominal pain, distension, change of bowel habit and change in the size of the stool. Patients with rectal cancer may manifest with symptoms of increased urge to defecate or a feeling of incomplete defecation.

It is important to note that two out of three cases which present symptoms are advanced and incurable, so it is better to have a lifestyle of regular check-ups as appropriate to prevent or detect cancer early.


Colorectal cancer is one of the easiest cancers to cure. Firstly it can be easily prevented as more than 99% of all colorectal cancers arise from pre-existing benign polyps. Detection and removal of these benign polyps will prevent - with absolute certainty - cancer forming in these patients. Even if colorectal cancer is found, early cancers have more than 95% chance of being cured. These are the Stage A cancers which are cancers located only at the Inner lining of the intestines and have not penetrated the muscle layers of the wall of the colon. These cancers are normally removed and treated by colonoscopic removal or surgery.

Stage B cancers are removed by surgery. Chemotherapy is needed if there are additional factors that may increase the risk of recurrence. Cancers with spread to the lymph nodes in the surrounding tissues are Stage C cancers. These patients will need surgery followed by a course of chemotherapy. In addition, rectal cancer patients with lymph nodes may need radiotherapy. Stage D or cancers with spread to other organs may need surgery for palliation or to lessen their symptoms and to control the spread of disease.

Currently I remove most cancers of the colon and rectum with laparoscopic surgery as this method hastens good recovery and has the same if not better long term cure rates than the usual open surgical removal of the cancer with a long incision on the abdomen. Robotic surgery is only needed in some cases of very low cancers of the rectum as access may be limited in normal laparoscopic surgery for some surgeons although a good laparoscopic surgeon will not have much problems with most cases even of very low rectal cancers.