By Dr Ananya Mandal, MD
Colorectal cancer is commonly termed bowel cancer. It usually begins in the large intestine and, depending on its starting point, colorectal cancer is sometimes called colon cancer or rectal cancer.
The primary site of the cancer
The cancer may begin as one or more polyps that eventually begin to grow into the wall of the colon or rectum. This then spreads to the walls and via the blood vessels or lymph vessels to nearby lymph nodes and then to distant parts of the body, such as the liver. Spread to distant parts of the body is called metastasis.
Symptoms of bowel cancer
There may be little or no symptoms at the initial stages of bowel cancer. This is what makes this cancer so dangerous.
There may be blood or mucus in the stools, an unexplained change in bowel habits with prolonged diarrhea or constipation, loss of appetite and unexplained weight loss. Cancer can sometimes start in the small bowel but this is rarer.
Colorectal cancer statistics
Colorectal cancer is the third most common cancer in the UK after breast and lung cancer. Around 40,000 new cases are detected each year. In addition, colorectal cancer is the second most common cause of cancer death in the UK. The incidence rate was 47.2 (29.4 colon, 17.8 rectum) per 100,000 population in the UK in 2008.
Two-thirds of bowel cancers develop in the colon, with the remaining third developing in the rectum. The rates are higher for men than women for both colon and rectal cancers. Most common ages affected by the cancer are those over the age of 65.
In the United States, excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women. The lifetime risk of developing colorectal cancer is about 1 in 20 (5.1%). Colorectal cancer is also the second leading cause of cancer-related deaths in the United States when both sexes are considered together.
Certain factors raise the risk of colorectal cancer. These include:
Age – most cases occur in individuals over age 65.
Gender – men are at a higher risk of colorectal cancer than women.
Diet – those who have a regular high proportion of fibre and low proportions of saturated fat have a lower risk of bowel cancer. A diet high in red or processed meats raises risk of bowel cancer.
The obese and overweight are at a greater risk of bowel cancer.
Those who lead a more sedentary life with little exercise are at a higher risk.
High alcohol intake and smoking raise risk of bowel cancer.
Family history and inherited conditions may raise the risk in some individuals .
Screening for bowel cancer
If detected early bowel cancer can be treated successfully. All individuals between the ages of 60 and 69 are offered bowel cancer screening every two years, and the screening programme is currently being extended in England to those aged 70 to 75.
Screening is carried out by taking a small stool sample and testing it for the presence of blood. This is called the faecal occult blood test or FBT. An extra screening test is being introduced over the next three years for all people at age 55. This test involves flexible sigmoidoscopy which involves looking for polyps and growths within the intestines with a flexible tube with a camera at its tip.
Treatment and prognosis
Bowel cancer can be treated using a combination of surgery, chemotherapy and radiotherapy. Some individuals may also benefit from biological therapy. If bowel cancer is diagnosed early, there is a greater chance of survival for at least 5 years after diagnosis than if diagnosed late.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)