September 10, 2009

Study Explores Overdiagnosis of Prostate Cancer


For every man who benefits from prostate cancer screening, many more are diagnosed and treated unnecessarily. The extent of this “overdiagnosis” of prostate cancer was explored in a study published in the Journal of the National Cancer Institute.

Each year in the United States, more than 192,000 men are diagnosed with prostate cancer and more than 27,000 die of the disease.

Men 50 years of age or older in the United States are often offered prostate-specific antigen (PSA) testing for the early detection of prostate cancer. The test may be offered at a younger age to men at high risk of prostate cancer. The PSA test measures proteins that are produced and shed by the prostate. PSA levels tend to be elevated when prostate cancer is present, but levels can also be elevated in benign (non-cancerous) conditions affecting the prostate.

A concern with the use of PSA testing is that it may identify some cancers that do not require treatment. This is sometimes referred to as “overdiagnosis.” Research suggests that some prostate cancers are very slow-growing and will not affect a man’s health during his lifetime. Diagnosis and treatment of these cancers exposes men to the complications of cancer treatment without providing a benefit.

To explore how frequently overdiagnosis has occurred since PSA screening became widespread in the United States, researchers evaluated information from a large, national cancer registry. They assessed prostate cancer trends from 1986 (the year before an influential PSA study was published) to 2005.

  • During the 30 years since the introduction of PSA testing, PSA testing has resulted in 1.3 million more prostate cancer diagnoses than would have occurred otherwise. Roughly one million of these men received treatment for prostate cancer.
  • The increase in prostate cancer diagnoses after the introduction of PSA testing was most apparent in younger men. Prostate cancer incidence rates have tripled in men in their 50s and increased by more than seven-fold in men younger than 50.
  • There has been a decline in prostate cancer mortality during the PSA screening era, but it’s unclear how much of this decline is due to screening (improvements in treatment are likely to have played a role as well). Nevertheless, even if all of the decline in mortality is due to screening, the results of this study suggest that relatively few men have benefited from early detection.

This study highlights the importance of an informed decision-making process about prostate cancer screening, in which men who are considering being screened fully understand what is known about the potential risks and benefits.

Reference: Welch HG, Albertsen PC. Prostate cancer diagnosis and treatment after the introduction of prostate-specific antigen screening: 1986-2005. Journal of the National Cancer Institute [early online publication]. August 31, 2009.

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