Tests after a diagnosis of colon or rectal cancer
If any of your biopsies show that there is cancer in the bowel, you will have more tests. These are to find out the size and position of the cancer and whether it has spread. This is called staging.
The results will help you and your doctor decide on the best treatment for you. Some tests may be repeated during and after treatment to check your progress. Your doctor or specialist nurse will explain this to you.
You will have blood tests to assess your general health.
Your blood may be tested for a protein called carcinoembryonic antigen (CEA). Some people with bowel cancer have higher levels of this protein. If your level of CEA is high, your doctors may check it regularly to see how well your treatment is working.
CT (computerised tomography) scan
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This test checks for any signs that the cancer has spread outside the bowel.
A CT scan takes a series of x-rays, which build up a three-dimensional picture of the inside of the body. The scan takes 10–30 minutes and is painless. It uses a small amount of radiation, which is very unlikely to harm you and will not harm anyone you come into contact with.
You will be asked not to eat or drink for at least four hours before the scan.
You may be given a drink or injection of a dye, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It’s important to let your doctor know if you are allergic to iodine or have asthma, because you could have a more serious reaction to the injection. You’ll probably be able to go home as soon as the scan is over.
Hear from a superintendent radiographer in CT, and Jyoti, a CT scan patient, about what to expect when having a CT scan.
This is a combination of a CT scan (see above) and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body.
A PET/CT scan may occasionally be done if more detailed information is needed after a CT scan. It may also be used to help the doctors plan treatment if there is cancer in the liver or lungs.
You won’t be able to eat for six hours before the scan, although you may be able to drink. A technician injects a small amount of mildly radioactive glucose (sugar) into a vein in your hand or arm. The radiation dose is very small. You then wait for the glucose to be absorbed by your body. After an hour or so you have the scan, which takes 30–90 minutes. The scan will show areas where the glucose has been absorbed. Cancers absorb more glucose than other parts of the body. This helps the doctors identify any areas of cancer. You can usually go home after the scan.
MRI (magnetic resonance imaging) scan
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An MRI scan can help doctors plan treatment if there is cancer in the liver.
The test uses magnetism to build up a detailed picture of areas of your body. The scanner is a powerful magnet, so you may be asked to complete and sign a checklist to make sure it’s safe for you. The checklist asks about any metal implants you may have, such as a pacemaker, surgical clips or bone pins. You should also tell your doctor if you’ve ever worked with metal or in the metal industry, as very tiny fragments of metal can sometimes lodge in the body. If you do have any metal in your body, it’s likely that you won’t be able to have an MRI scan. In this situation, another type of scan can be used.
Before the scan, you’ll be asked to remove any metal belongings including jewellery. Some people are given an injection of dye into a vein in the arm, which doesn’t usually cause discomfort. This is called a contrast medium and can help the images from the scan to show up more clearly.
During the test, you’ll lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It’s painless but can be slightly uncomfortable, and some people feel a bit claustrophobic. It’s also noisy, but you’ll be given earplugs or headphones. You can hear, and speak to, the person operating the scanner.
Endorectal ultrasound scan (ERUS)
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This test may be used to help plan your operation. Ultrasound scans use sound waves to build up a picture of body tissues. An endorectal ultrasound scan can show the size and location of a cancer in the rectum.
For the test, you lie on your left side with your knees bent up. A nurse or doctor gently passes a small, lubricated probe into the back passage. This produces an image of the rectum on a screen.
The scan takes about 10 minutes and you can usually go home as soon as it’s over.
Waiting for your test results
It will probably take several days to a couple of weeks for the results of your tests to be ready. The results of the tests will show the grade and the stage of the cancer. This information will be used by a team of doctors and nurses, known as the multidisciplinary team or MDT, to decide on the most appropriate treatment.
Waiting for results can be a difficult time. It may help to talk things over with a friend or relative. You can also contact one of our cancer support specialists or one of the organisations listed in the further resources section.