Further tests for bowel cancer
If any of the general tests or tests to find cancer in the bowel show you have bowel cancer, you will have additional tests to see if the cancer has spread to other parts of your body. Before any test, ask how much you will have to pay.
Learn more about these additional tests:
Your blood may be tested for a protein produced by some cancer cells. This is called a tumour marker. The most common tumour marker for bowel cancer is called carcinoembryonic antigen (CEA).
If the results of the blood test show that you have a high CEA level, your doctor may organise more tests. This is because other factors, such as smoking or pregnancy, may also increase the level of CEA. If your CEA level is high, it will be retested after treatment to see if it has returned to normal. Not all bowel cancers have a raised CEA.
A CT (computerised tomography) scan uses x-ray beams to take many pictures of the inside of your body and then compiles them into one detailed, cross-sectional picture. You might have a CT scan of your chest, abdomen and the area between your hip bones (pelvis) to see if the cancer has spread. A scan is usually done as an outpatient. Most people can go home as soon as the test is over.
Your doctor will give you instructions about eating or drinking before a CT scan. As part of the procedure, a dye is injected into a vein to make the pictures clearer. This dye may make you feel hot all over and leave a strange taste in your mouth for a few minutes. You might also feel that you need to urinate (pee or wee), but this sensation won’t last long.
During the scan, you will lie on a table that moves in and out of the CT scanner, which is large and round like a doughnut. Your chest, abdomen and pelvis will be scanned to check if the cancer has spread to these areas. The scan takes 5–10 minutes and is painless.
Before having scans, tell the doctor if you have any allergies or have had a reaction to dyes during previous scans. You should also let them know if you have diabetes or kidney disease or are pregnant.
An MRI (magnetic resonance imaging) scan uses a powerful magnet and radio waves to create detailed, cross-sectional pictures of the inside of your body. Usually only people with cancer in the rectum have an MRI; it is not commonly used for cancers higher in the bowel. An MRI may also be used to scan the liver if any abnormality seen on a CT scan needed further investigation.
A dye might be injected into a vein before the scan to help make the pictures clearer. During the scan, you will lie on a treatment table that slides into a large metal tube that is open at both ends. The noisy, narrow machine makes some people feel anxious or claustrophobic. If you think you could become distressed, mention it beforehand to your medical team. You may be given a medicine to help you relax and you will usually be offered headphones or earplugs.
The MRI scan may take between 30 and 90 minutes, depending on the size of the area being scanned and how many images are taken.
A positron emission tomography (PET) scan combined with a CT scan is a specialised imaging test. The two scans provide more detailed and accurate information about the cancer. A PET–CT scan is most commonly used before surgery to help find out where the cancer has spread to in the body. It can also be used after surgery to check if the cancer has come back after treatment.
Before the scan, you will be injected with a glucose solution containing a small amount of radioactive material. Cancer cells show up brighter on the scan because they take up more glucose solution than the normal cells do. You will be asked to sit quietly for 30–90 minutes as the glucose spreads through your body, then you will be scanned. The scan itself will take around 30 minutes. Let your doctor know if you are claustrophobic as the scanner is a confined space.
Medicare covers the cost of PET–CT scans for bowel cancer only in limited circumstances. If this test is recommended, check with your doctor what you will have to pay.
If you are diagnosed with advanced bowel cancer, your doctor may test the biopsy sample for genetic changes that can cause the cancer cells to behave differently. These tests may look for mutations in the RAS and BRAF genes, or features in the cancer cells suggesting that further genetic testing is required.
Your treatment team can use the results of molecular testing to tell them what treatment may work for you and which treatment won’t work. For example, some targeted therapy drugs do not work for people with a RAS gene mutation. See Systemic treatment for more details.
Podcast: Tests and Cancer
A/Prof David A Clark, Colorectal Surgeon, Royal Brisbane and Women’s Hospital, and The University of Queensland, QLD, and The University of Sydney, NSW; A/Prof Siddhartha Baxi, Radiation Oncologist and Medical Director, GenesisCare Gold Coast, QLD; Dr Hooi Ee, Specialist Gastroenterologist and Head, Department of Gastroenterology, Sir Charles Gairdner Hospital, WA; Annie Harvey, Consumer; A/Prof Louise Nott, Medical Oncologist, Icon Cancer Centre, Hobart, TAS; Caley Schnaid, Accredited Practising Dietitian, GenesisCare, St Leonards and Frenchs Forest, NSW; Chris Sibthorpe, 13 11 20 Consultant, Cancer Council Queensland; Dr Alina Stoita, Gastroenterologist and Hepatologist, St Vincent’s Hospital Sydney, NSW; Catherine Trevaskis, Gastrointestinal Cancer Specialist Nurse, Canberra Hospital, ACT; Richard Vallance, Consumer.
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