Cancer Screening Overview (PDQ®)   What Is Cancer Screening?
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.   Screening tests include the
following:   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 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.
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.  Screening test res