Screening tests help find some types of cancer before you have any symptoms. That means you have them even if you feel fine and you have a healthy lifestyle. They’re part of your regular medical care.
If you’re part of a certain age group or population in Canada, you can go for regular screening tests that can help find breast, cervical and colorectal cancer at such an early stage that you won’t have noticed that anything is wrong. Some screening tests can even help prevent cancer by finding changes in your body that would become cancer if they were left untreated.
Talk to your doctor to learn more about your risk of cancer and what screening tests you should have. Be sure to mention any family history of cancer. A family history of certain cancers may mean your risk is higher than normal. Your doctor may suggest testing at an earlier age or using a different test than recommended by the provincial guidelines.
What makes a good screening test
No screening test is 100% accurate, but a good screening test is one that results in a decrease in death rates in people with cancer.
Researchers also look for other benefits of screening including improved quality of life or less harmful treatments as a result of finding the cancer early.
The World Health Organization (WHO) suggests reviewing several factors before introducing a test as a screening tool for the general population. These include:
- Sensitivity – How effectively the test identifies people who actually have cancer.
- Specificity – How often a test gives negative (normal) results for people who do not have cancer.
- Acceptability – Will the population who will benefit the most from the test (the target population) agree to be tested by this method.
Benefits and risks of screening
Almost every test or procedure has benefits and risks. When you think about how important it is to find cancer early, we believe the benefits of having regular screening tests for breast, cervical and colorectal cancer outweigh the risks.
But before having any test, it’s important to be aware of the risks so that you’re making an informed decision that’s right for you.
Benefits of regular screening
- Better survival rates – In most cases, the earlier a cancer is detected, the better your chance of survival.
- Better quality of life – Early detection may also mean less treatment and less time spent recovering.
Risks of regular screening
- False positive results – When test results suggest cancer even though cancer is not present. False positives can result in anxiety, stress and possibly painful and unnecessary tests to rule out cancer (that is, to make sure you don’t have cancer when the screening test has suggested you might).
- False negative results – When cancer is not detected by the test even though it is present. False negative results can cause you or your physician to ignore other symptoms that indicate the presence of cancer, causing a delay in diagnosis and treatment.
- Over-diagnosis – Some cancers would not necessarily lead to death or decreased quality of life.
- Increased exposure to harmful procedures, for example, very low doses of radiation from x-ray tests.
Tests can be used for diagnosis and screening
Some tests that are used for screening can also be used to diagnose or rule out cancer in people who have reported symptoms to their doctors. For example, mammograms are used both for screening women with no signs of breast cancer and helping to diagnose (or rule out) cancer in women who have signs of breast cancer.
Your doctor will be able to explain what type of test you are having and why you are having the test.