Screening Benefits and Risks

Almost every test or procedure carries benefits and risks. The important thing is to be aware of them so that you can make an informed decision that is right for you.

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.

BENEFITS OF REGULAR SCREENING

  • Earlier detection of cancer: In most cases, the earlier a cancer is detected, the better your chance of survival. Early detection may also mean less treatment and less time spent recovering.
  • Reducing the anxiety of "not knowing": Many people prefer to have ‘check-ups’, just like a physical exam with your family doctor.     

RISKS OF REGULAR SCREENING  

  

  • False positive results. A false positive test result occurs if test results suggest cancer is present even though it is not.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. A false negative test result occurs if 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. For example, some prostate cancers never become clinically apparent, meaning that they do not cause any symptoms, nor do they affect life expectancy or quality of life. Men with these tumours may not ever develop symptoms or need treatment for cancer.
  • Increased exposure to harmful procedures. Almost every test or procedure carries benefits and risks, for example, very low doses of radiation from x-ray tests. Talk to your doctor to learn more about what your risks may be.   

WHAT MAKES A GOOD SCREENING TEST 

 

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?  

TESTS THAT 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 can be used for both screening and diagnostic purposes:

  • To screen women with no signs of breast cancer, or
  • To help diagnose women who do have signs of breast cancer (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.