BOWEL CANCER. Causes of bowel cancer

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1 A cancer is an abnormality in an organ that grows without control. The growth is often quite slow, but will continue unabated until it is detected. It can cause symptoms by its presence in the organ or in another organ if some of the cancer cells break off and start to grow in a second site (called a secondary or metastasis). Bowel cancer is the most common internal cancer in Australia. It occurs in the large bowel, which includes the colon and the rectum. The colon is the part of the large bowel that is in the tummy, starting on the right side where the small bowel ends and the appendix attaches. The colon then goes up towards the chest, across the upper tummy and down the left side of the abdomen. The colon ends at the top of the pelvis (about 15cm from the anus) when the large bowel becomes the rectum. The rectum is the name of the last 15cm of large bowel above the anus. It is situated in the pelvis. Colorectal cancer is second in incidence to breast cancer in women and prostate cancer in men, but if both sexes are counted together, bowel cancer holds the unwanted first position. Bowel cancer is the second most common cause of cancer death in Australia behind lung cancer. Bowel cancer is thought to grow from benign growths called polyps (See Colonic Polyps). If a polyp is removed at colonoscopy, the pathway to bowel cancer is disrupted. If a bowel growth has become cancerous it will require an operation. The operations for bowel cancer are discussed in Rectal Resection for cancer and Laparoscopic bowel surgery. Causes of bowel cancer No one is certain exactly why cancer forms in the bowel. There are several abnormalities in the genes of bowel cancer cells leading to many theories to describe the progression from normal bowel cells, to abnormal but benign polyp cells, to malignant bowel cancer cells. Bowel cancer is much more common in Western countries and many risk factors have been identified that relate to a Western lifestyle, including diet, exercise, obesity, alcohol and smoking. These are discussed in more detail in the section of the website entitled Primary prevention of bowel cancer. Bowel cancer can also run in families, but only about 1 in 6 patients with a newly diagnosed bowel cancer will have a family history of the disease. Some families have a very high incidence of bowel cancer, so much so that these hereditary conditions are given names, such as Familial Adenomatous Polyposis (FAP) and Hereditary Non-polyposis Colorectal Cancer (HNPCC) or the Lynch Syndrome. Symptoms of Bowel Cancer Bleeding from the bowel ANY bleeding from the bowel is abnormal. It should be reported to a doctor and consideration given to investigation to find the cause. This often means a colonoscopy to assess the whole colon and rectum. Bleeding from the bowel can be due to benign anal causes such as haemorrhoids and anal fissures but it is very risky to presume this, as any new bleeding may also be due to bowel cancer or polyps.

2 Blood that is a darker colour, blood that is mixed in with the stool and bleeding that is associated with other symptoms such as a change in bowel habit are of particular concern. Change in bowel habit Most people have a regular bowel habit that is established early in adult life. The normal frequency of bowel actions is between 3 times a day and 3 times a week. A change in the bowel habit can have many less concerning causes, including changes in medications, the use of pain relief, antibiotics and bowel infections. Nevertheless, a consistent change in the way a person s bowel works over a few weeks or months is cause for concern and should be discussed with a doctor. It is likely that a colonoscopy will be recommended. Abdominal pain Unexplained abdominal pain warrants investigation. If it is sudden the investigation will take the form of blood tests and Xrays, such as a CT scan. A colonoscopy is sometimes needed when no cause can be found or if there is an abnormality in the large bowel on the CT scan. Rarely a bowel cancer may present with abdominal pain. This may be due to the cancer itself (if it is big enough), it may cause pain by pressing on or invading other organs or it may partially block the bowel. A colonoscopy will establish this cause of the pain. Abdominal mass Occasionally a mass will be felt in the abdomen, especially in slim people. An abdominal mass can also be found on a CT scan performed for some other reason. A colonoscopy will need to be performed to establish whether the mass is coming from the bowel. Symptoms of anaemia (low blood count or low haemoglobin) Small amounts of blood loss over a long period of time can cause a lowering of the red blood cell count, or anaemia. Minor levels of anaemia are sometimes unexpectedly found on routine blood tests. More significant anaemia can cause symptoms such as tiredness, lethargy and shortness of breath with exercise. Anaemia has many causes, but slow blood loss is the most common, and the colon and rectum are the most common source of such bleeding. A colonoscopy should be considered whenever anaemia is found. Weight loss Unexplained weight loss has many causes as well. Colonoscopy is not the first line of investigation in such situations, but may have a role if other investigations are negative. Stages of Bowel Cancer Bowel cancer develops slowly from the inside layer of the bowel lining (the mucosa). Whilst it is contained in the mucosa it is not actually a cancer but rather an adenomatous polyp. It can be cured if it is completely removed by polypectomy during a colonoscopy. If this abnormality then grows through the layers of the bowel wall it has become a bowel cancer. From here it can spread to the local lymph nodes or even to other organs, particularly the liver and the lungs.

3 The prognosis of bowel cancer is closely related to the stage of the disease at diagnosis. Cancer prognosis is defined in terms of 5 year survival, that is the chance of being alive and free of cancer 5 years after the cancer was first diagnosed and treated. Bowel cancer staging can be quite complicated, but can also be simplified down to 4 stages, A, B, C and D. Stage A Bowel Cancer Stage A means that the cancer has either not reached the muscle of the bowel wall, or has grown into but not through this muscle. This stage has the best prognosis, with a 5 year survival of 95%. Surgery is usually all that is required, with chemotherapy hardly ever considered for this stage of cancer. Stage B Bowel Cancer Stage B is a bit more advanced than Stage A. The cancer has spread through the muscle of the bowel wall towards the outside surface of the bowel, but has not spread anywhere else. The 5 year survival for Stage B bowel cancer is about 80%. Surgery is usually the only treatment, although chemotherapy is sometimes used in Stage B bowel cancer if there are other concerning features under the microscope. Stage C Bowel Cancer In Stage C bowel cancer, the primary tumour can be at any level, but there has been spread to the local lymph nodes. Lymph nodes are nearby to all tissues in the body and help to mop up a pale fluid called lymph that can be left behind in the tissues. Cancer tends to spread to lymph nodes before it goes to other organs. Having cancer in the local lymph nodes significantly worsens the prognosis, and Stage C bowel cancer has a 5 year survival of about 60% if surgery alone is offered as treatment. Most people with Stage C bowel cancer therefore undergo 6 months of chemotherapy, which lifts the 5 year survival rate up towards that seen with Stage B. Stage D Bowel Cancer Stage D bowel cancer means that the cancer has spread to other organs. This is most commonly to the liver, but spread can also be to the lungs, to the inside of the tummy cavity or to other organs more rarely. Surgery to the bowel primary alone cannot cure the cancer in this situation, and chemotherapy and/or surgery to the other organ(s) will be required. The best prognosis is with a limited number of secondary deposits that can be safely removed from the liver or lungs, but even so, the 5 year survival for this group is about 15%. Investigation of Bowel Cancer Colonoscopy Colonoscopy is the most common investigation used to diagnose bowel cancer. All patients should have a complete colonoscopy (if possible) prior to bowel cancer surgery. A sample of the abnormality (biopsy) will be taken at the time of the colonoscopy and sent to a laboratory. Blood Tests Several blood tests will need to be performed, mainly to confirm that it is safe to proceed to major surgery. These will include, but may not be restricted to, the following; > Complete Blood Picture (CBP) Checks the level of red blood cells, white blood cells and platelets > Electrolytes Checks the levels of the important salts in the body, especially sodium,

4 potassium and chloride > Kidney Function Tests > Liver Function Tests > Group and Save Tests for blood type so that blood can be prepared for transfusion if required during or after surgery. Blood transfusion is quite rare with bowel surgery unless the patient is anaemic (low red blood cell count) when the diagnosis of bowel cancer is made. As well as the above standard tests, surgeons often test for a bowel cancer marker called carcinoembryonic antigen or CEA. This blood test is often used to make sure that a cancer has not come back in the years after surgery. The initial CEA level will act as a baseline. CT (Computed tomography) Scan of chest/abdomen and pelvis A CT scan is a computerised Xray that shows very accurate images of the organs in the chest and tummy. It allows assessment of the primary tumour itself as well as allowing your surgeon to check that there are no secondaries in the liver or lungs. A CT scan is a standard part of the preoperative workup for any bowel cancer surgery, whether the cancer is in the colon or the rectum. MRI (Magnetic Resonance Imaging) of pelvis Patients with a rectal cancer will be asked to have an MRI scan. This scan gives even closer information about how far the tumour has spread in the local area and whether there are large lymph nodes that may also have cancer in them. A locally advanced rectal cancer (Stage B or C) is best treated with chemotherapy and radiotherapy before surgery. People who have hip or knee replacements or a pacemaker are unable to have an MRI scan due to the magnetic nature of the machine. Treatment of Bowel Cancer Surgery Surgery is the mainstay of treatment for bowel cancer. The cancer, healthy bowel on either side of the cancer and the draining lymph nodes needs to all be removed and the bowel joined back together (if possible). It is major surgery, whether it is done using an abdominal cut or a keyhole technique. Colorectal Surgery website has further discussion of the procedures performed by colorectal surgeons for bowel cancer. Chemotherapy Chemotherapy is the use of cancer killing drugs to help reduce the chances of the cancer coming back in the 5 years after surgery. Patients with advanced colon cancer (Stage C and D, and some Stage B) should receive 6 months of chemotherapy after they have recovered from the bowel surgery. After the operation, the bowel that is removed will be sent to a pathologist who will examine it under a microscope. This report is sent to the surgeon, who will involve a chemotherapy specialist (oncologist) if required. Bowel cancer chemotherapy is often well tolerated and does not cause many side effects. Nausea and diarrhoea are not uncommon, but hair loss is rare. Radiotherapy Radiotherapy is the use of high powered radiation to kill cancer cells. As mentioned above, locally advanced rectal cancer has a better outcome if treated by radiotherapy and chemotherapy before surgery. The decision to give this treatment is usually based on the images from an MRI scan.

5 Although most pre-operative chemo/radiotherapy is long course, occasionally a short course of radiotherapy only will be given. This involves 5 days of intensive treatment followed by an operation within a few days. Long course chemo/radiotherapy involves 25 sessions of radiotherapy over a 5 week period, with chemotherapy being given through a vein at the same time. The patient then waits 8 to 10 weeks for the full effect of the treatment to take effect (and for tissue swelling to settle) before surgery is undertaken. The remaining courses of chemotherapy are given after recovery from surgery. Follow up after bowel cancer surgery After discharge from hospital, your surgeon will arrange an appointment in the rooms a few weeks down the track, to check that recovery has been complete and no late complications or worries have occurred. If no post-operative chemotherapy is required, the next appointment will be at 3 months after the operation. If chemotherapy is required, you will usually be left in the care of your oncologist until this treatment is finished. The timing of subsequent consultations will vary from surgeon to surgeon. A common practice is to review the patient every 3 months for the first 2 years and every 6 months for post-operative years 3, 4 and 5. Colonoscopy If a full colonoscopy cannot be performed before the surgery, it will be scheduled between 3 and 6 months after the procedure. If the full colonoscopy has been done, the next one will be 12 months after the surgery. If this colonoscopy is normal, subsequent colonoscopies will occur about every 3 years. If polyps are found, the frequency of colonoscopy follow up may increase. Other tests Research has shown that patients do better if there is an intensive follow up process in the first few years after bowel cancer surgery. The exact protocol will differ from surgeon to surgeon, but a common example of a follow up protocol is as follows; CT scan of chest/abdomen and pelvis 1 year, 2 years and 3 years after surgery. CEA blood test (see above) 3 monthly starting one year after surgery for the second and third years.