Colorectal Cancer
What is colorectal cancer?
Colorectal cancer is a cancer of the colon or rectum. It is also known as bowel cancer. It is a specific type of cancer known as adenocarcinoma, which means that the mucus glands of the colon become malignant.
What is a cancer?
A cancer occurs when some cells become abnormal and grow out of control. It is due to some of the genes in that cell becoming abnormal. The normal protective factors stop working, the abnormal cells multiply and the tumour becomes larger, eventually becoming symptomatic and spreading.
What is a tumour?
A tumour is another word for a lump. Colorectal cancers are malignant tumours.
What does malignant mean?
Malignant means cancer. All colorectal cancers are malignant.
How are the colon and rectum different?
The colon and rectum form the large bowel. The rectum is the end 20-30cm of the colon ending at the anus. They are the same organ but cancers of the rectum are sometimes more complicated and require different treatment. The cancers in the rectum and colon are exactly the same otherwise. The only difference is location in the large bowel.
What is the large bowel?
The large bowel or large intestine, begins where the small bowel ends and ends at the anus. There is about 6m of small bowel and about 1.5m of large bowel. All nutrients are absorbed by the small bowel, the large bowel is only responsible for absorption of water and salt and is not essential for life.
How much large bowel can be removed?
All of the large bowel can be removed safely but usually a only a small section is removed.
Is bowel cancer a “bad” cancer?
There is no such thing as a good cancer in any organ in any part of the body. Bowel cancer is serious and if left untreated is always fatal. However when adequately treated the overall results for bowel cancer are quite good and many patients can be cured.
How does bowel cancer spread?
All the cancers begin in the lining of the bowel wall. There is progressive spread through the different layers of the bowel. Eventually the cancer can spread into the lymph nodes of the colon and then the cancer can get into the blood stream and spread to other organs. The common organs to which the cancer can invade are the liver and lungs.
What are lymph nodes?
Lymph nodes are collections of white blood cells, which help fight infection and cancer. There are lymph nodes throughout the human body. The lymph nodes for the affected part of the colon are removed as part of the surgery for bowel cancer.
Is bowel cancer common?
Yes, bowel cancer is the second commonest cancer in both women and men. The only commoner cancers are breast and prostate cancer. Approximately 1 in 15 Australians will get a bowel cancer. The incidence increases with age and the average age to develop bowel cancer is 65.
What causes bowel cancer?
Mostly the cause is unknown. 1 in 5 patients will have a family history of bowel cancer. Bowel cancer is commoner in Western countries with diets high in protein (meat) and low in fibre. Even migrants from low risk countries will have the same risk for bowel cancer as Australian born patients within 25 years. The remainder of the cancers are due to unknown environmental factors. It is never solely the result of a “bad diet” or lifestyle but due to a number of factors that we have little understanding of.
Cancers all begin as polyps and having polyps is a risk factor for getting bowel cancer. There are some conditions that cause many polyps and these patients have a much higher risk.
What are the symptoms of bowel cancer?
Many bowel cancers have no symptoms at all and are picked up during screening. There may be anaemia (low blood count) due to bleeding that is sometimes unseen.
Common symptoms are bleeding, change in bowel habit (new onset constipation or diarrhoea), abdominal pain or a mass and weight loss.
Sometimes there are more urgent presentations with large volume bleeding or bowel obstruction.
How to screen for bowel cancer?
The best test for detection of bowel cancer is a colonoscopy but this is an invasive test with potential side effects. Because bowel cancer is common other tests have been developed to check for bleeding. The test is known as the faecal occult blood test (FOBT). The Australian government sends out screening kits to all people on the electoral roll beginning at the age of 50 and 5 yearly thereafter.
What is the FOBT?
This is checking for microscopic bleeding in the stool. The kit requires placement of a small amount of faeces onto a testing strip. If it is positive for blood a colonoscopy is required.
It is not a perfect test and does not replace the need for investigations if there are symptoms and the test is negative. It is important to understand that the test is specifically designed for patients with no symptoms whatsoever.
Patients with symptoms of any sort or with other indications for colonoscopy (such as family history of bowel cancer) need to have a colonoscopy and should not need a FOBT.
What does a positive FOBT mean?
The risk of bowel cancer with a positive FOBT is less than 10%. The commonest cause for a positive FOBT is colonic polyps (around 30%). Up to 50% of patients will have no abnormal findings at colonoscopy.
What are colonic polyps?
Colonic polyps are growths in the lining of the colon, some are precancerous but most are not.
Is a family history of bowel cancer important?
The importance of a family history is dependant on how many family members are affected and their age. The more members affected and the younger the age the higher the risk. 1 in 5 people with bowel cancer have a family history.
Some families have a known genetic predisposition to bowel cancer. Patients in these families tend to develop the cancers at an earlier age and often have different non-bowel cancers in the family as well. At risk families undergo specific genetic tests.
What tests are required for bowel cancer?
Most cancers are found at colonoscopy either during screening or as part of investigation for symptoms.
Once a cancer is found patients require staging with CT scanning and some blood tests. Rectal cancer requires specific staging with MRI or endoanal ultrasound.
Patients will also likely require additional tests to plan for surgery such as heart and lung tests.
How is bowel cancer treated?
Almost all patients require surgery. Even if the cancer has spread to other organs, surgery is often required to prevent the cancer causing symptoms such as bleeding or obstruction.
The surgery involves removal of part of the colon.
Rectal cancer sometimes requires preoperative treatment with radiotherapy to shrink the cancer and make the surgery more successful.
Some patients require post operative chemotherapy depending on the stage of the cancer.
All aspects of the treatment will be discussed with the patient in detail.
Are there any alternative treatments available?
Surgery gives the best chance of cure. Sometimes the cancer is more aggressive and spreads beyond the bowel. There are several treatments available. Surgery, radiotherapy and chemotherapy are proven, evidence based procedures.
Even for patients that cannot be cured, there are several treatments that prolong quality and quantity of life. The main advances in medicine have been in this area.
What about non-medical and complimentary treatments?
All treatment given by medical doctors is evidence based and proven. There are several non medical practitioners who claim to treat cancer, but none are scientifically valid. If their treatments were proven, they would be part of mainstream medicine.
Patients should exercise caution when planning their treatment and always discuss plans or concerns with their doctors. It is important to be well informed when choosing your medical treatment and always consult a qualified medical practitioner who will have the necessary training and experience in treating cancer patients.
What is the follow up after treatment for bowel cancer?
All patients will be followed up individually after their treatment. The tests depend on the stage of the cancer and what treatment was given. Generally, patients will need repeat colonoscopies, CT scans, blood tests and clinical evaluation.
