Cancer Screening Overview (PDQ®)–Patient Version

What Is Cancer Screening?

KEY POINTS

Cancer screening is looking for cancer before a person has any symptoms.
There are different kinds of screening tests.
Screening tests have risks.
- Some screening tests can cause serious problems.
- False-positive test results are possible.
- False-negative test results are possible.
- Finding the cancer may not improve the person's health or help the person live longer.

Cancer screening is looking for cancer before a person has any symptoms.

Screening tests can help find cancer at an early stage, before symptoms appear. When abnormal tissue or cancer is found early, it may be easier to treat or cure. By the time symptoms appear, the cancer may have grown and spread. This can make the cancer harder to treat or cure.

It is important to remember that when your doctor suggests a screening test, it does not always mean he or she thinks you have cancer. Screening tests are done when you have no cancer symptoms.

There are different kinds of screening tests.

Screening tests include the following:

Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
Laboratory tests: Medical procedures that test samples of tissue, blood, urine, or other substances in the body.
Imaging procedures: Procedures that make pictures of areas inside the body.
Genetic tests: A laboratory test in which cells or tissue are analyzed to look for changes in genes or chromosomes. These changes may be a sign that a person has or is at risk of having a specific disease or condition.

Screening tests have risks.

Not all screening tests are helpful and most have risks. It is important to know the risks of the test and whether it has been proven to decrease the chance of dying from cancer.

Some screening tests can cause serious problems.

Some screening procedures can cause bleeding or other problems. For example, colon cancer screening with sigmoidoscopy or colonoscopy can cause tears in the lining of the colon.

False-positive test results are possible.

Screening test results may appear to be abnormal even though there is no cancer. A false-positive test result (one that shows there is cancer when there really isn't) can cause anxiety and is usually followed by more tests and procedures, which also have risks.

False-negative test results are possible.

Screening test results may appear to be normal even though there is cancer. A person who receives a false-negative test result (one that shows there is no cancer when there really is) may delay seeking medical care even if there are symptoms.

Finding the cancer may not improve the person's health or help the person live longer.

Some cancers never cause symptoms or become life-threatening, but if found by a screening test, the cancer may be treated. There is no way to know if treating the cancer would help the person live longer than if no treatment were given. In both teenagers and adults, there is a rare risk of attempted or actual suicide in the first year after being diagnosed with cancer. Also, treatments for cancer have side effects.

For some cancers, finding and treating the cancer early does not improve the chance of a cure or help the person live longer.