Detection and Staging of Prostate Cancer

Early detection of prostate cancer is critical to successful treatment. The digital rectal exam (DRE) and the Prostate-Specific Antigen (PSA) blood test are the two most common methods of detecting prostate cancer.

A DRE is a gloved-finger examination of the prostate through the rectum. The PSA test is a blood test that is used to help screen for prostate cancer. The only conclusive form of detection is biopsy. This is usually done with the aid of ultrasound.

To detect prostate cancer early, the American Cancer Society advises that all men over 50 have an annual prostate DRE and a PSA blood test. However, many recommend that those at high-risk (African-American men and those men with a family history of prostate cancer) should begin testing several years earlier.

To perform a digital rectal exam (DRE), a doctor briefly inserts a gloved, lubricated finger into the rectum to feel the back wall of the prostate. Most of the prostate cannot be felt, but by feeling the back wall, a doctor can tell if there are areas of firmness, hard nodules or lumps. These may show a problem since the prostate is supposed to feel soft, smooth and round. However, an abnormality does not always mean that cancer is present.

The prostate specific antigen (PSA) blood test is used to check the enzyme normally produced by the prostate cells. PSA is not found in large amounts anywhere else in the body. A small amount of PSA normally leaks into the blood stream and can be detected with a simple blood test.

Higher levels of PSA can be associated with inflammation, enlargement or prostate cancer. In other words, a mild to moderate increase in PSA does not always mean cancer. Often a higher PSA level can show that the prostate cancer is in its later stages and may have spread. Together, the PSA blood test and digital rectal exam are used as tools to detect cancer early. If the doctor is concerned by the results of these tests, then an ultrasound and biopsies are done.

A lubricated ultrasound probe is placed into the rectum and ultrasound waves are sent out from the probe to obtain a picture of the prostate. This procedure allows the entire prostate to be seen to determine the prostate size and to see if problems are present. It also allows more accurate biopsy of areas for concern.

An ultrasound alone is not completely precise since at least 30 percent of the time cancer can be present, but not detected by the ultrasound. Therefore, biopsies are generally done even when the ultrasound appears normal.

To take a biopsy of the prostate, many tiny sliver-like pieces of tissue are removed using a long thin needle to be looked at under a microscope to see if cancer is present. The procedure takes only 15 minutes and usually causes only mild discomfort.

When a doctor finds prostate cancer, he or she will determine the extent of the disease. This is called "staging." The doctor may use various diagnostic tests, imaging, and other tests to find out whether the cancer has spread, and if so to which location. The stage of the disease will help determine treatment options.

All prostate cancers are minimally described by two characteristics: grade and stage. While grade and stage are correlated, they are independent ways of assessing the potential behavior of a cancer.

Grade is a description of the cancer cells as they appear under a microscope and is assigned by a pathologist; the most common form of prostate cancer grading is the Gleason grading system.

Prostate cancer is composed of cells of varying shapes. Dr. Donald Gleason characterized prostate cancer cell shape and described categories, which provide some assessment of risk of cancer stage (how extensive the cancer is) and survival. The Gleason score is a sum of the two most prevalent patterns detected by the pathologist and ranges from 2, the least aggressive, to 10, the most aggressive.

Stage is a description of the extent of growth of a cancer and is assessed by various means, such as physical examination and bone scans. Prostate cancer is staged commonly with the TNM system. T refers to the size of the primary tumor. N will describe the extent of lymph node involvement and M refers to the presence or absence of metastases.