Bowel cancer: Causes, Symptoms and Treatments

Bowel cancer is the umbrella term for cancer that develops in the large bowel.  It is the fourth commonest cancer in the UK. Every year over 41,000 people are diagnosed with bowel cancer. Depending on its origin, it may be referred to as colon cancer or rectal cancer. In the UK, 54% of cases of bowel cancer are preventable. One of the most common types of cancers diagnosed, it usually affects people over the age of 60.

What causes bowel cancer?

Although the exact cause of bowel cancer is unknown, there are a number of risk factors that can greatly increase an individual’s chance of developing the disease. These include:

• Diet – Nearly 25% of all bowel cancer cases in the UK are associated with the consumption of eating red and processed meat, whilst 12% of cases consume too little fibre. Foods such as eggs, sugars, cheese, and animal fat also increase the risk of bowel cancer.
• Age – Around 6 out of 10 bowel cancer patients are over the age of 70
• Weight – 13% of cases of bowel cancer are overweight
• Alcohol – People who consume between 1.5 and 6 units of alcohol per day are 17% more likely to develop bowel cancer
• Tobacco – 8% of bowel cancer cases in the UK have been linked to smoking
• Family history – People are more at risk of developing bowel cancer at some point in their lives if they have a close family member who has had the disease before the age of 50. There are some rare inherited conditions that pre-dispose to bowel cancer such as Familial Polyposis syndrome
• Bowel polyps – benign adenoma polyps can lead to bowel cancer. The purpose of screening programmes is to identify and remove polyps to prevent later bowel cancer.
• Medical problems – diabetics are more likely to develop bowel cancer

Bowel cancer screening

Early detection of bowel cancer can result in better outcomes and increased chance of cure.

• Patients aged between 60 and 74 are invited to participate in the national screening programme. This involves sending in a poo sample for analysis
• If blood is detected in the sample then patients are invited to attend for investigation of the lower bowel.
• There are many causes for blood in the poo and most patients will not have cancer and therefore be reassured.

If cancer is found it is hoped that it will have been discovered early and therefore have better outcomes after treatment.

What are the main symptoms of bowel cancer?

The most common symptoms of bowel cancer include:

• Rectal bleeding
• Constant pain in the lower abdomen, swelling, or discomfort
• Constant blood in the stools
• A change in bowel habit
• Fatigue
• Unexplained loss in weight

In many cases, these symptoms of bowel cancer are synonymous with other conditions. Blood in stools, for example, if accompanied by pain, may be caused by haemorrhoids. However, it is always advisable to see a specialist, if these kinds of symptoms persist beyond the three week mark.

In some cases, a person may demonstrate no symptoms of bowel cancer, hence the reason screening is so important for people over the age of 60.

Diagnosis of bowel cancer

After referral to a specialist the relevant investigations will be arranged based on the presenting symptoms and the initial out-patient consultation and examination

Initial Consultation:

• History of presenting symptoms
• Relevant past medical history and family history
• Physical examination – this may include inspection of the rectum with sigmoidoscope (small plastic telescope)

Special investigations:

• Colonoscopy – to visualise the lining of the bowel and biopsy any abnormalities, polyps can be removed at the same time
• CT Colonography – is a good diagnostic tool but colonoscopy may still be needed to take biopsies and/or remove polyps identified by the scan

Staging Investigations – if cancer is diagnosed then the specialist will arrange scans to assess the size and possible extent or spread of the cancer, these will include one or all of the following, depending on the area in the bowel in which the cancer was found.

• CT scan
• MRI scan
• CT-PET scan
• Endo-anal ultrasound

Read more: testing for colon cancer

Bowel cancer treatment

Bowel cancer treatment depends on how advanced it is, and where in the large bowel it is located. All treatments are tailored to the individual patient. The decisions about treatment are made at a Multi-Disciplinary Team Meeting (MDT). At the meeting the surgeon, oncologist, radiologist and pathologist all discuss each case to ensure the best treatment option is recommended. All cancer cases should be discussed through an MDT.

The usual forms of treatment for bowel cancer are:

• Surgery – Surgery is the most effective way of treating colorectal cancer and in many cases no further treatment will be needed. Surgery involves removing the cancerous growth from the colon or rectum. Surgery can be done either laparoscopically (keyhole) or open. The surgeon will explain the best way to remove the tumour and the possible side-effects and consequences of any proposed operation. Some operations will result in the need for a colostomy bag and if this is the case the surgeon will explain why.  

• Chemotherapy / radiotherapy – These modalities may be used in different ways in the treatment of colorectal cancer. Firstly chemotherapy may be given after surgery in more advanced cancers to increase the chance of cure. Sometimes chemotherapy may be given first to help shrink a large tumour before surgery, this is usually done in conjunction with radiotherapy. This chemo-radiotherapy combination is most commonly used for rectal cancers. In more advanced cancers chemotherapy may be used in what is known as a palliative setting. In this case the chemotherapy will hope to halt the progression of the cancer when it is accepted that a cure is unlikely.

In some cases a combination of all the different treatments may be used to destroy the cancer. The earlier the cancer is diagnosed, the higher the chances that treatment will be a success. It is important to realise that treatment is tailored specifically to each individual patient based on that patient`s own medical history, the type and extent of cancer and the various treatment modalities that are available.

Read more: Late-stage bowel cancer

Follow up after bowel cancer treatment

After treatment for bowel cancer, patients will be followed and monitored using a combination of CT scan, blood tests and colonoscopies, done at intervals. This is to monitor for any signs of recurrence of disease as not all patients will be cured. If recurrence is detected this can allow further treatment to be considered.