Bowel Cancer (Colorectal Cancer)
What is Bowel Cancer?
Cancer occurs where normal cells in the body, through genetic changes, lose the ability to control and regulate growth. As cancers grow, they can invade tissue around them (local invasion). Through further genetic changes, cancers can also spread more widely, often first to local lymph nodes then to distant organs such as the liver or lungs. These are known as metastases or secondaries.
Bowel cancer is a growth of abnormal cells that line the bowel, generally the colon and rectum. Small bowel cancers are very rare. Untreated, bowel cancers continue to grow and can spread locally to adjacent organs such as the bladder and stomach, or distally to lymph nodes and then usually the liver.
How common is Bowel Cancer?
Bowel cancer is the 2nd most common cancer in Australia. More than 16,000 new cases are diagnosed each year in Australia and 4,000 deaths. It is responsible for nearly 10% of all cancer related death.
What causes Bowel Cancer?
The underlying cause relates to cumulative genetic mutations in the cells lining the bowel. Bowel cancer is more common in developed countries and it is thought that the processed, low fibre foods we eat slow the transit of stool through the colon, exposing the cells to cancer producing substances for longer (carcinogens). There are a number of other risk factors for developing bowel cancer including:
Age. More than 90% of people are over 40. The risk doubles every decade from here.
Family history of colorectal cancer or polyps
Personal history of polyps (bowel cancers develop from polyps although not all polyps will turn into cancer)
Inflammatory bowel disease (risk of cancer is related to the amount of colon involved, the severity of the disease and the amount of time with the disease)
Genetic conditions where there are multiple polyps (includes FAP - familial adenomatous polyposis, and Lynch Syndrome)
What are the symptoms?
The most common symptoms are rectal bleeding and changes in the bowel habit. These are common symptoms that can be caused by a range of conditions but should always prompt a visit to the local doctor and referral for a colonoscopy to check for bowel cancer. Abdominal or rectal pain and weight loss are usually late signs. Iron deficiency anaemia should always alert the doctor to look for a gastrointestinal cancer usually colon. Many bowel cancers especially on the right side may not cause any symptoms until quite late.
How can I reduce my risk of bowel cancer?
There are a number of ways to reduce the risk of bowel cancer. These include:
Limit your alcohol intake; less than 2 standard drinks/day
Maintain a healthy diet; high in fruit and vegetables, low in processed foods and red meat
Exercise regularly; 30 minutes of brisk activity per day
Maintain healthy weight; avoid obesity, aim for a body mass index <25.
Avoid smoking; increases the risk of many cancers including colorectal cancer
Attend bowel screening; a ‘bowel test’ involves testing the stool for occult or hidden blood (FOBT). It is recommended all Australians aged between 50 and 74 undergo bowel screening using FOBT every 2 years. This is available through your local doctor as part of the national bowel cancer screening program (NBCSP).
What tests do I need?
If your doctor suspects that you have bowel cancer, a referral to a colorectal surgeon may be organised. Your local doctor or surgeon may perform the following tests:
Examination including abdominal and internal examination (rectal examination)
Blood tests including haemoglobin, liver function tests and the tumour marker for bowel cancer (CEA)
MRI scan – should be routine for all rectal cancers to help decide on the best treatment options.
How is Bowel Cancer treated?
Colorectal cancer requires surgery in almost every case to cure the disease. Some rectal cancers may benefit from radiotherapy and chemotherapy before surgery. If the cancer has spread to the liver or lungs, it is often not curable and chemotherapy is often used. If all of the cancer cannot be removed, this is called palliative chemotherapy. Sometimes, even if the cancer has spread to the liver or lungs, a cure is still possible with a combination of chemotherapy and surgery to the bowel cancer and sites of secondaries/metastases.
What are the prospects of cure?
When detected early, bowel cancer has a very high cure rate. The overall outcome will depend of the stage of the disease at presentation and you general health. Approximately 75% of all patients will be cured with surgery +/- chemotherapy.
What is the follow up after treatment?
Your surgeon will arrange a schedule of follow-up usually for 5 years after treatment of your cancer. This helps to identify problems that may arise and identify recurrent disease early. Follow up will include examination in the rooms and sometimes under anaesthetic, colonoscopy and imaging such as MRI, CT and sometimes PET scans.