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Prostate Cancer

What is it? Who gets it?

The human male’s prostate gland is the walnut-sized, semen-producing organ that wraps around the urethra below the bladder. The prostate is prone to develop prostate cancer, which ranks as one of the top four cancers in North America, together with lung, breast (in women) and colorectal cancer. In the United States about one in every six men will be diagnosed with prostate cancer in their lifetime, or about 250,000 new cases of prostate cancer per year. About 30,000 men die of the disease.1

Causes of prostate cancer

Scientists really do not know what causes prostate cancer, which is partly genetic and partly environmental. Prostate cancer numbers vary strikingly. It is most common in the United States and Western Europe; it is uncommon in Japan and in Asia generally.

Some risk factors for prostate cancer:

  • Age over 50.
  • African-American men develop prostate cancer at a higher rate than any other US group.
  • Men whose fathers, sons or brothers are diagnosed with prostate cancer are more likely to develop the disease, especially if the disease is diagnosed before age 60.
  • High fat diet may be linked to development of prostate cancer.

Cancer Facts and Figures from the American Cancer Society, 2005:

  • Ninety percent of all prostate cancer diagnosed is local/ regional.2
  • Five year relative survival local/regional prostate cancer is 100%.2
  • Five year relative survival for advanced metastatic prostate cancer is 33.5%.3

Screening

Whether or not healthy asymptomatic men should be screened with tests for the presence of prostate cancer is a controversial subject. Men should be aware of the risks and the potential benefits before they ask for or consent to screening.

The most common screening test for prostate cancer is the Prostate Specific Antigen (PSA) test. PSA is a protein produced by prostate cells. A PSA test measures blood levels of PSA on the theory that a diseased prostate elaborates more PSA into the bloodstream. PSA levels may (or may not) increase well above normal in men with prostate cancer. The PSA test is imperfect; it is a test plagued by false positive and false negative results. Some men whose PSA levels are normal may in fact have prostate cancer due to a false negative PSA test result. These men will be falsely reassured. On the other hand, some men whose PSA is high, may not have prostate cancer due to a false positive PSA test result. If a PSA level is abnormally high a biopsy will be required to confirm results and check for cancer. Biopsy of the prostate is uncomfortable and there is risk of infection.

Despite problems with screening tests, demand for such tests is quite high. In 2003 some 45 million PSA tests were carried out worldwide, representing a global market of US $400 million.4

References

  1. American Cancer Society. Detailed Guide: Prostate Cancer. [ link ]
  2. American Cancer Society. Cancer Facts and Figures. 2005. [ link ]
  3. US National Cancer Institute. Surveillance Epidemiology End Results. Cancer Stat Fact Sheets. Prostate Cancer. [ link ]
  4. Zakroff J. Molecular diagnostics for cancer on the rise. IVD Technology. Jan-Feb 2003. [ link ]