Large Bowel Cancer

What is large bowel cancer?

Large bowel cancer is the disease that develops when the cells lining the colon or the rectum multiply uncontrollably. Cancers of the colon and the rectum together are called colorectal cancer.

The disease may cause no symptoms in its early stages. Screening therefore matters for people in the appropriate age group who have no complaints. Besides catching cancer early, screening also makes it possible to remove some polyps before they turn cancerous.

How does it develop?

A significant proportion of large bowel cancers develop from polyps that form on the lining of the bowel. Not every polyp is a cancer. But some adenomas and serrated lesions can accumulate cellular changes over the years and turn into cancer.

Finding and removing a polyp during colonoscopy can interrupt this process. The pathology result is used to determine the type of the polyp and the timing of the next check.

Who is at higher risk?

Risk increases with age. Besides this:

• Large bowel cancer or an advanced polyp in a first-degree relative,
• Having previously had a polyp or large bowel cancer,
• Hereditary syndromes such as Lynch syndrome or familial adenomatous polyposis,
• Long-standing ulcerative colitis or Crohn’s colitis,
• Smoking, high alcohol consumption, excess weight and physical inactivity,
• A diet rich in processed meat and poor in fibre

can increase the risk. Having a risk factor does not mean that cancer will certainly develop; nor does the absence of risk factors make screening unnecessary.

What are the symptoms?

Large bowel cancer can also be found without causing any symptoms at all. The complaints that may be seen are:

• Red blood in the stool or dark-coloured stool,
• Constipation, diarrhoea, or a new and persistent change in the form of the stool,
• A feeling of not having emptied completely after opening the bowels,
• Unexplained abdominal pain or bloating,
• Iron deficiency anaemia, tiredness and pallor,
• Unintentional weight loss.

These symptoms can also have commoner, non-cancerous causes. Even so, complaints that are new or persistent should be assessed.

Heavy bleeding from the back passage, black tarry stool, fainting, severe and increasing abdominal pain, persistent vomiting, or an inability to pass wind or stool require emergency assessment.

At what age does screening start?

In people at average risk, regular screening is recommended to begin at 45.

That is also the age given in the diagram at the head of this page. The international guidelines point the same way: the USPSTF recommends screening between 45 and 75, and between 76 and 85 leaves the decision to the person’s health status and previous screening history.

Türkiye’s national population-based screening programme, for its part, invites the 50–70 age group among people at average risk and without complaints; it includes a faecal occult blood test every two years and a colonoscopy every ten years. So the age at which the programme calls someone in is not the same as the age at which screening is recommended to begin — the programme calls at 50, the recommendation is 45.

Where there is a family history, a hereditary syndrome, inflammatory bowel disease, a previously found advanced polyp or a symptom already present, assessment begins without waiting for either age and is planned for the individual.

Screening is for people who have no symptoms. Where there is blood in the stool, unexplained iron deficiency or a persistent change in bowel habit, diagnostic assessment is needed without waiting for any particular age.

What are the methods of screening?

The screening options include:

• Faecal occult blood or faecal immunochemical testing (FIT),
• Colonoscopy,
• Stool DNA tests in suitable patients,
• Computed tomography colonography,
• Flexible sigmoidoscopy.

Each method has a different interval, benefit and limitation. Where a stool test is positive, a diagnostic colonoscopy is needed.

How is the diagnosis made?

Where there is a suspicious complaint or test result, the main examination is usually colonoscopy. During colonoscopy the lining of the bowel is assessed and a biopsy is taken from any suspicious area. The definitive diagnosis is made by examining the tissue in a pathology laboratory.

Where cancer is found, blood tests and imaging such as computed tomography may be carried out to determine how far the disease has spread. In rectal cancer, additional examinations such as pelvic magnetic resonance imaging may be needed.

How is it treated?

Treatment is planned according to the position of the tumour in the colon or the rectum, its stage, its biological features and the person’s general health. The options may include:

• Endoscopic removal,
• Surgery,
• Chemotherapy and targeted drugs,
• Immunotherapy,
• Radiotherapy, especially in rectal cancer.

The plan is most often formed by gastroenterology, general surgery, medical oncology, radiation oncology, radiology and pathology specialists assessing the case together.

What can be done to reduce the risk?

Taking part in appropriate screening is one of the most effective steps. Besides this, staying away from smoking, limiting alcohol, moving regularly, keeping to a healthy weight, and adopting a diet rich in vegetables, fruit, whole grains and fibre can help to reduce the overall risk.

This page is for general information; speak to your doctor about your own screening or treatment plan.