Bowel cancer is the most common internal cancer affecting both genders in Australia and is second only to lung cancer as a cause of cancer related death.
On average one in 19 Australian men and one in 27 Australian women will develop colorectal cancer by the age of 75 years. Colorectal cancer (CRC) is mostly seen in people aged 40 years and over and from age 50 years its incidence rises sharply.
Australia, like the USA, has one of the highest incidence rates of colorectal cancer in the world. The USA has already adopted colorectal cancer screening on a national basis. In Australia, there are about 11,000 new cases of colorectal cancer each year and about 5,500 deaths from the disease.
What is Colorectal Cancer?
Colorectal cancer is an uncontrolled, malignant (destructive) growth of the mucosal (lining) cells of the colon (large intestine) or the rectum.
These cancer masses grow rapidly without regard to the usual control mechanisms of the body, invade local adjacent structures, may cause bowel obstruction or spread to distant parts of the body (metastases) where they may disrupt function of other organs such as the liver.
Colorectal cancer frequently ulcerates and bleeds. Often microscopic bleeding is present long before the patient develops symptoms. This interval before any symptoms become evident is the period where screening tests for colorectal cancer are most indicated as it is the window of opportunity to effect the only known cure of the disease by resecting (surgically removing) the cancer.
Regular (Bowelscan recommends yearly) screening of persons at risk provides the best chance of detecting the intermittent bleeding from these early cancers or polyps.
As with all cancers, colorectal cancer progresses in stages. In its earliest stages, colorectal cancer is one of the most curable cancers, with predictions of a 95% chance for a five year survival in stage 1, as opposed to only a 3% in stage 4.
What is a Polyp?
A polyp is a small often rounded mass of growing cells of the intestinal lining and thought to represent the earliest stages of colorectal cancer development.
Cells making up the polyp are usually benign adenomas (non-malignant) but a small percentage may, over a 5 to 10 year period, become cancerous. Polyps, like cancers, may bleed.
What are the symptoms of Colorectal Cancer?
During the early stages of colorectal cancer development, when the tumour is either a small benign polyp or small cancer, there are usually no symptoms. Yet this early stage of the disease is where the best outcomes are achieved in population screening by programs such as Bowelscan.
The cancer begins almost always as a non-malignant projection from the bowel wall known as a polyp, or adenomatous polyp. The process of change from a polyp to a cancer is slow – taking up to 10 years. Most, but not all, polyps and cancers bleed from time to time. Bleeding from polyps and early cancers may not be visible, but can be detected by a simple chemical test of bowel motions. Procedures that detect and remove polyps and early cancers can be expected to reduce deaths from cancer.
The obvious symptoms of possible bowel cancer are:
- visible blood in the toilet bowl following a bowel movement;
- rectal bleeding;
- persistent change in bowel habits, eg constipation or diarrhoea;
- abdominal pain.
If any of these symptoms are evident people should consult their doctor without delay.
More facts about bowel cancer
- The incidence of bowel cancer has not fallen over the past 20 years.
- Cancer of the bowel, or colorectal cancer, is the most common internal cancer affecting Australians.
- The lifetime risk of developing cancer in the bowel is 1 in 24.
- The chance of contracting bowel cancer increases progressively from the age of 40.
- It is predicted that there will be 11,000 cases of bowel cancers diagnosed in Australia annually.
- Around 5,500 deaths from bowel cancer will occur in Australia each year.
- Deaths from this cancer each year are double the national road toll.
- You increase the risk of bowel cancer 2 to 3 times if you have one or more close relatives who have had colorectal cancer or polyps.
- There may be no obvious symptoms of bowel cancer until the cancer has reached an advanced stage.
- Once symptoms of bowel cancer have developed, the chance of long term survival is roughly halved.
- 90% of bowel cancers can be cured if detected early.