Some screening tests are used because they have been shown to be helpful both in finding cancers early and in decreasing the chance of dying from these cancers. Other tests are used because they have been shown to find cancer in some people; however, it has not been proven in clinical trials that use of these tests will decrease the risk of dying from cancer.
Scientists study screening tests to find those with the fewest risks and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) decreases a person's chance of dying from the disease. For some types of cancer, the chance of recovery is better if the disease is found and treated at an early stage.
Clinical trials that study cancer screening methods are taking place in many parts of the country. Information about ongoing clinical trials is available from the
Regular screening of women between the ages of 25 and 60 years with the Pap test decreases their chance of dying from cervical cancer. In women younger than 25 years, screening with the Pap test may show changes in the cells of the cervix that are not cancer but lead to further testing and possibly treatment. Screening with the Pap test is not helpful in women older than 60 years who have had recent negative Pap tests.
A Pap test is a procedure to collect cells from the surface of the cervix and vagina. A piece of cotton, a brush, or a small wooden stick is used to gently scrape cells from the cervix and vagina. The cells are viewed under a microscope to find out if they are abnormal. This procedure is also called a Pap smear. A new method of collecting and viewing cells has been developed, in which the cells are placed into a liquid before being placed on a slide. It is not known if the new method will work better than the standard method to reduce the number of deaths from cervical cancer.
After certain positive Pap test results, an HPV DNA test may be done to find out if the HPV infection that is causing the abnormal cells is one that is linked to cervical cancer. In women aged 30 or older, the HPV DNA test and the Pap test are used to screen for HPV infection. In women younger than 30 years, HPV infections are common but usually do not last long or cause problems.
Screening clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the