Cancer occurs when cells in the body begin changing and multiplying out of control. These cells can form lumps of tissue called tumors. Cancer that starts in the prostate is called prostate cancer. Cancer can grow and spread beyond the prostate, threatening health and life.
Understanding the Prostate
The prostate is a gland about the size and shape of a walnut. It surrounds the upper part of the urethra in men, the tube that carries urine from the bladder. The prostate produces most of the semen in which sperm travel. During orgasm, semen exits the body through the urethra.
When Prostate Cancer Forms
As a man ages, his prostate may change. Inside a changing prostate, groups of cells may form tumors or other growths. Some may be benign (not cancerous), but they may still cause symptoms. Others may be cancerous.
Noncancerous growths. As a man ages, the prostate may grow larger. This condition is called benign prostatic hyperplasia (BPH). Extra prostate tissue often squeezes the urethra, causing symptoms such as difficulty urinating. But BPH does NOT lead to cancer.
Atypical cells (prostatic intraepithelial neoplasia, or PIN). Some cells don't appear normal, but they are not cancer. These cells may indicate that cancer is present or is likely to form.
Cancer. Abnormal cells form a tumor (a lump of cells that grow uncontrolled). Cancer may or may not produce symptoms. Some tumors can be felt during a physical exam, others can't.
Cancer spread. Prostate cancer may spread to nearby organs. In some cases, the cancer spreads further, to bones or organs in distant parts of the body. This is called metastasis
Diagnosing Prostate Cancer
Prostate cancer may not cause symptoms at first. Urinary problems often are not a sign of cancer, but of another condition. To find out if you have prostate cancer, your doctor must examine you and order tests. Tests help confirm a diagnosis of cancer. They also help give more information about a cancerous tumor. Tests include:
Prostate specific antigen (PSA) testing: PSA is a chemical made by prostate tissue. The PSA level (amount of PSA in the blood) is tested to evaluate a man's risk for prostate cancer. In general, a high or rising PSA level may mean an increased cancer risk. PSA testing is also used to evaluate the success of cancer treatments.
Core needle biopsy: This test involves taking tissue samples from the prostate to provide more information about cancer cells. During the test, a small probe is inserted into the rectum as you lie on your side. This lets an image of your prostate be seen on a video monitor. With this image as a guide, the doctor uses a thin needle to remove tiny tissue samples from the prostate. You are given medications so you don't feel pain during the test.
FAQ: Prostate Cancer Screening
Q: Can prostate cancer be found before a man has symptoms?
A: Yes. Prostate cancer screening is looking for the disease before a person has any symptoms. Two screening tests commonly used to detect prostate cancer in the absence of symptoms are the digital rectal exam (DRE), in which a doctor feels the prostate through the rectum to find hard or lumpy areas, and a blood test that detects a substance made by the prostate called prostate-specific antigen (PSA). Together, these tests can detect many "silent" prostate cancers that have not caused symptoms. Due to the widespread use of PSA testing in the United States, approximately 90 percent of all prostate cancers are currently diagnosed at an early stage, and, consequently, men are surviving longer after diagnosis.
Q: How reliable are the screening tests for prostate cancer?
A: Neither of the screening tests for prostate cancer is perfect. Most men with an elevated PSA level do not have prostate cancer (false positives), and some men with prostate cancer have a low PSA level (false negatives). The DRE is also associated with false positives and false negatives. Using the DRE and PSA together will miss fewer cancers (greater sensitivity) but also increases the number of false positives and subsequent biopsies in men without cancer (lower specificity).
The National Cancer Institute's (NCI) Early Detection Research Network (EDRN) has a Prostate Collaborative Group that is exploring a variety of strategies to find better ways to detect prostate cancer early. In addition, NCI's prostate cancer Specialized Program of Research Excellence (SPORE) is funding projects to identify new diagnostic and prognostic biological markers, or biomarkers, of prostate cancer besides PSA.
Q: Does prostate cancer screening save lives?
A: The benefits of screening and local therapy (surgery or radiation therapy) for early prostate cancer remain unclear, and it is not known for certain whether prostate cancer screening saves lives. Because of this uncertainty, NCI, which is part of the National Institutes of Health, is supporting research to learn more about screening for prostate cancer. Currently, researchers are conducting a large randomized clinical trial, called the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, to determine whether screening with PSA tests and DREs reduces the death rate from this disease. The researchers are also assessing the risks of screening. Specifically, men who have an elevated PSA level or a suspicious DRE are more likely to have a biopsy, which is an invasive procedure, and, if the biopsy is positive, the risks of surgery, radiation therapy, and even active surveillance (also called watchful waiting) must be taken into account.
Initial results from the PLCO trial showed that annual PSA testing for 6 years and DRE testing for 4 years (performed in the same years as the first four PSA tests) did not reduce the number of prostate cancer deaths through a median follow-up period of 11.5 years (range 7.2 to 14.8 years) (2). At 7 years of follow-up, a point in time when follow-up of the participants was essentially complete, 23 percent more cancers had been diagnosed in the screening group than in the control group, in which men were randomly assigned to "usual care." These results suggest that many men were diagnosed with, and treated for, cancers that would not have been detected in their lifetime without screening and were consequently exposed to the potential harms of unnecessary treatments, such as surgery and radiation therapy. Nonetheless, it remains possible that a small benefit from the earlier detection of these "excess" cancers could emerge with longer follow-up. Therefore, follow-up of the PLCO participants will continue until all participants have been followed for at least 13 years.
In contrast, initial results from another large randomized, controlled trial of prostate cancer screening, called the European Randomized Study of Screening for Prostate Cancer (ERSPC), found a 20 percent reduction in prostate cancer deaths associated with PSA testing every 4 years (3). At the time the results were reported, the participants had been followed for a median of 9 years. The average number of PSA tests per participant in ERSPC was 2.1. Most participating centers in this trial used a lower PSA cutoff value as an indicator of abnormality than was used in the PLCO trial (3.0 nanograms per milliliter versus 4.0 nanograms per milliliter). As in the PLCO trial, many more cancers were diagnosed in the screening group than in the control group. The ERSPC researchers estimated that 1,410 men would have to be screened and 48 additional cancers would have to be detected to prevent one death from prostate cancer.