Screening for Prostate Cancer

What is screening?

Screening for cancer is examination (or testing) of people for early stages in the development of cancer even though they have no symptoms. Scientists have studied patterns of cancer in the population to learn which people are more likely to get certain types of cancer. They have also studied what things around us and what things we do in our lives may cause cancer. This information sometimes helps doctors recommend who should be screened for certain types of cancer, what types of screening tests people should have, and how often these tests should be done. Not all screening tests are helpful, and they often have risks. For this reason, scientists at the National Cancer Institute are studying many screening tests to find out how useful they are and to determine the relative benefits and harms.

If your doctor suggests certain cancer screening tests as part of your health care plan, this does not mean he or she thinks you have cancer. Screening tests are done when you have no symptoms. Since decisions about screening can be difficult, you may want to discuss them with your doctor and ask questions about the potential benefits and risks of screening tests and whether they have been proven to decrease the risk of dying from cancer.

If your doctor suspects that you may have cancer, he or she will order certain tests to see whether you do. These are called diagnostic tests. Some tests are used for diagnostic purposes, but are not suitable for screening people who have no symptoms.

Prostate Cancer Screening

The prostate is a gland in males that is involved in the production of semen. It is located between the bladder and the rectum. The normal prostate gland is the size of a walnut and surrounds the urethra, the tube that carries urine from the bladder.

Risk of prostate cancer

Prostate cancer is the most common cancer in North American men (other than skin cancer). It is the second leading cause of cancer death in men (after lung cancer). Both the number of new cases of prostate cancer and the number of deaths due to prostate cancer have increased in the past decade.

Anything that increases a person's chance of developing a disease is called a risk factor. Some of these risk factors for prostate cancer are as follows:

Age - Prostate cancer is rarely seen in men younger than 50 years old. The chance of developing prostate cancer increases as men get older.

Race - Black males are more likely to develop prostate cancer than white males. Black males are also more likely to die of prostate cancer than white males.

Family History of Prostate Cancer - A man whose father, brother, or son has had prostate cancer has a higher-than-average risk of developing prostate cancer.

Other potential risk factors include alcohol consumption, vitamin or mineral interactions, and other dietary habits.

Screening tests for prostate cancer

Digital Rectal Examination - A digital rectal examination (DRE) is performed by a doctor during a regular office visit. For this examination, the doctor inserts a gloved finger into the rectum and feels the prostate gland through the rectal wall to check for bumps or abnormal areas. Although this test has been used for many years, whether DRE is effective in decreasing the number of deaths from prostate cancer has not been determined.

Transrectal Ultrasonography - During this examination, high-frequency sound waves are sent out by a probe about the size of the index finger, which is inserted into the rectum. The waves bounce off the prostate gland and produce echoes that a computer uses to create a picture called a sonogram. Doctors examine the sonogram for echoes that might represent abnormal areas. Whether ultrasonography is effective in decreasing mortality from prostate cancer has not been determined.

PSA - For this test, a blood sample is drawn and the amount of prostate- specific antigen (PSA) present is determined in a laboratory. PSA is a marker that, if present in higher than average amounts, may indicate prostate cancer cells. However, PSA levels may also be higher in men who have noncancerous prostate conditions. Scientists are studying ways to improve the reliability of the PSA test.

Because unnecessary treatment due to false screening results could be harmful, research is being done to determine the most reliable method for prostate cancer screening. For example, scientists at the National Cancer Institute are studying the value of early detection by DRE and PSA on reducing the number of deaths caused by prostate cancer.

Source: National Cancer Institute, National Institutes of Health, November 2000