Prostate cancer screening

Prostate cancer screening involves a combination of a digital rectal exam (DRE) and a prostate-specific antigen (PSA) blood test. Supplemental diagnostic tools are also available, such as transrectal ultrasound.


Anatomy
The prostate gland is a male gland located at the base of the bladder. It's normally the size of a walnut. The prostate surrounds the urethra (the tube that carries urine from the bladder out through the penis) and the neck of the bladder. The prostate and other smaller glands produce fluids that combine with sperm to make semen. The size of the prostate increases with age and in response to infections or tumors of the prostate.

Causes of prostate cancer
The cause of prostate cancer is unknown. Some studies seem to indicate that eating a diet high in fat, especially animal fat, increases the risk of prostate cancer. Researchers are currently studying genetic and other possible causes, including environmental factors. A family history of prostate cancer in a brother or father doubles the risk of developing the disease. The more relatives you have who've been diagnosed with prostate cancer, the greater your risk. The risk also increases as you get older, especially after age 50. (About three out of four men with prostate cancer are diagnosed after age 65.) For unknown reasons, African-American men have twice the risk of developing prostate cancer than Caucasian men. They're also more likely to be diagnosed at a more advanced stage of cancer and have poorer survival rates. Recent studies have shown no increased risk for prostate cancer after a vasectomy.

Purpose/indications
Researchers haven't agreed on when, or even if, routine prostate cancer screening should be done. Very small prostate cancers may not cause a man any problems, yet the treatments for prostate cancer (such as surgery or radiation) may have unwanted side effects. Prostate cancer is often a very slow-growing cancer, and so far there's no evidence that early diagnosis and treatment improve the chance of living longer.
The American Cancer Society's (ACS) prostate cancer screening guidelines recommend that beginning at age 50, both the PSA test and the digital rectal exam be offered yearly to men who have a life expectancy of at least 10 years. The ACS also recommends yearly screening beginning at age 45 for men who have a high risk for prostate cancer. (You're considered high risk if you're African American or have two or more first-degree relatives -- such as a father, brother or son -- who've had prostate cancer.)

Other medical organizations have their own recommendations. Some recommend giving men enough information to make an informed decision, while others don't recommend screening. The U.S. Preventive Services Task Force doesn't recommend for or against routine screening, since there is currently insufficient data to make any conclusion regarding the benefits of screening. Until research proves there is no benefit to screening, however, many doctors will continue to recommend routine testing.


When to consult your doctor
It's important to discuss your personal risks and screening needs with your doctor. You may want to consider regular screening if you're over age 50. The test may be appropriate at age 45 if prostate cancer runs in your family or you're African American. You may consider routine screening unnecessary if you're under age 50 and have no symptoms, or you're age 75 or older and have other conditions that may limit your life span to less than 10 years.
Keep in mind that prostate cancer is often diagnosed before symptoms appear. During the early stages, most men don't notice any symptoms. If symptoms do appear, they'll vary depending on the tumor's size, location and how far it has advanced. Symptoms may include:

difficulty starting or stopping urine flow
more frequent urination, especially at night
urgent need to urinate
decreased force or interrupted flow of the urinary stream
inability to urinate
painful or burning urination
painful ejaculation
erectile dysfunction (difficulty having or sustaining an erection)
blood in the urine or semen
pain in the lower back, pelvis or upper thighs
swelling in the lower legs

What to expect
Prostate cancer treatment is based on how far the cancer has advanced, making an accurate diagnosis extremely important. The doctor may use a variety of tests to help make a diagnosis, including:
Digital rectal exam: The prostate gland is located next to the rectum and can be felt through the rectal wall. During a digital rectal exam, the doctor uses a gloved, lubricated finger to feel the prostate gland for lumps or other abnormalities. It's possible to feel tumors larger than ½ inch in diameter.

Prostate-specific antigen (PSA): The PSA blood test measures prostate-specific antigen, a protein made only by the prostate gland. Small amounts of this protein can normally be found in a man's blood. Many factors can influence PSA levels. For example, PSA blood levels often rise when the prostate is enlarged or traumatized, or you have an infection or prostate cancer. A few men with prostate cancer have a normal PSA, while some men who don't have prostate cancer have a high PSA. The test can't be used by itself to make a diagnosis, but it may be used in combination with a digital rectal exam of the prostate. In fact, using the two tests together can lead to significantly improved cancer detection rates.The PSA test should precede the DRE, however, since rectal manipulation can elevate the PSA level in the blood.

Transrectal prostatic ultrasound (TRUS): If screening indicates the possibility of prostate cancer, your doctor may do a TRUS. Using sounds waves from a special probe inserted into the rectum, this test creates an image of the prostate gland. TRUS can help your doctor identify any suspicious areas of the gland that may be candidates for biopsy (taking a tissue sample for further examination). As with the PSA and DRE tests, the TRUS is not perfect and can't be used alone to make a definite diagnosis of cancer.

Core needle biopsy: A biopsy of the tissue (with TRUS guidance) is needed to confirm the presence of cancer cells. The biopsy typically involves inserting a small needle into the rectum, which then goes through the rectal wall into the prostate. It can also be done by inserting the needle through the skin between the scrotum and the anus. Local anesthetic may be used. Several samples are usually taken for microscopic examination by a pathologist. The biopsy is used to make the actual diagnosis and grade the tumor.

Percent-free PSA: The typical PSA test is a measure of the total PSA level in the blood and is relatively low in sensitivity for detecting prostate cancer. New research is showing value in comparing the total PSA level to the free PSA in the blood (or the PSA unattached to blood proteins). It's thought that a free-to-total PSA ratio will help differentiate benign from malignant prostate conditions. Researchers have noted that more PSA is attached (and, likewise, less of the PSA is free) in cases of malignant prostate conditions. The percent-free PSA test may help decrease the number of biopsies done for false-positive PSA readings. Other testing methods include age-adjusted PSA, PSA velocity and PSA density (PSDA).
If a biopsy confirms a diagnosis of prostate cancer, treatment options will be discussed. You may need additional tests -- such as X-rays, an MRI or CT scan, a bone scan or a lymph node biopsy -- to determine whether the cancer is localized or has spread (metastasized) beyond the prostate.


Benefits and risks of prostate cancer screening
Currently, PSA testing is the only blood test used for prostate cancer screening. The test is inexpensive and can detect cancers before symptoms develop or cancers that a digital rectal exam may miss. When used in combination with a digital rectal exam, early detection of prostate cancer significantly increases. Five-year survival rates are as high as 98 percent if the cancer is discovered at a localized stage.

Risks
False-positive results are possible, which can cause anxiety and lead to more testing, such as an unnecessary biopsy. False-negative readings are also possible, which can create false reassurance and a failure to detect cancer in the early stages. Additional risks to consider:
The sensitivity of a DRE is limited. Tumors may occur in portions of the prostate that can't be palpated by the doctor. A small tumor, such as a stage A tumor, will likely go undetected.
Small elevations of PSA are hard to interpret. Infections and benign conditions of the prostate can also cause elevations.
Very high readings are reliable in indicating cancer, but tumors at that stage are usually large with advanced cancer.
Screening may help detect cancer at an early or localized stage, but cannot predict which men will benefit from surgery.
PSA detection of prostate cancer has not been shown to prolong life. If prostate cancer is diagnosed, there is no standard recommended treatment. Treatment options vary with age, stage and grade of the cancer, along with individual preferences.
Detection of prostate cancers that would not cause symptoms before death from other causes may subject some men to emotional distress and inappropriate treatment.

Considerations
Elevations in PSA levels can be related to many other conditions or treatments, including:
benign prostatic hypertrophy or hyperplasia (noncancerous prostate enlargement)
acute and chronic prostate inflammation
rectal manipulation (Your doctor may collect blood before a digital rectal exam or 48 hours after the exam.)
surgical procedures of the prostate gland
bladder catheterization (inserting a flexible tube into the bladder to inject or remove fluid)
vigorous prostate massage
recent ejaculation (Your doctor may suggest avoiding sexual activity for two days before testing.)
Generally, PSA levels of four and below are considered normal. The PSA level considered normal varies by age and risk group, however. Your doctor may try to increase the accuracy of cancer detection by using reference ranges specific to your age and risk group. For example, reference ranges allow for the increased incidence of benign prostatic hypertrophy in aging men. Alternate methods for analyzing PSA, such as percent-free PSA, PSA velocity and PSA density (PSDA), are also being used to increase accuracy. If you have an abnormal PSA, one of these methods may be used to help determine if you need a biopsy. The usefulness of these methods is still being evaluated. So far there is no evidence that early diagnosis and treatment will improve the chance of surviving prostate cancer, so not all doctors routinely use these tests. Ask your doctor for details.