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>  News Releases >   2003 >   March

Cancer testing is out of balance, study says

Posted 03/22/03, by Andy Nordhoff

Researchers recommend more screening for colorectal cancer and less for prostate cancer

Cancer screening practices do not always follow scientific evidence, a Dartmouth Medical School study shows.

Researchers found that a significantly higher percentage of men are screened for prostate cancer than for colorectal cancer, despite the fact that prostate screening has not been proven to reduce prostate cancer deaths while colorectal screening can substantially reduce the mortality from colon and rectal cancer.

The study provides the first national population-based estimates of rates of screening with PSA (prostate-specific antigen) — the blood test for prostate cancer — and compared the extent U.S. men undergo PSA screening to colon cancer screening. While there is widespread agreement in the medical community that men (and women) should be screened for colon cancer annually starting at age 50, there is no consensus about whether men should be screened for prostate cancer.

"We wanted to see if medical practice reflects scientific evidence," said lead author Brenda Sirovich, assistant professor of medicine at DMS and the VA Outcomes Group in White River Junction, Vt. The study appears in the March 19 issue of The Journal of the American Medical Association, co-authored by Lisa Schwartz and Steven Woloshin, also assistant professors of medicine at DMS and members of the VA outcomes group.

The results were surprising, said Sirovich. "We anticipated that if medical care was in line with scientific evidence, then the proven test — colorectal cancer screening — would be more common than the unproven prostate cancer screening. This was not the case. More men had been tested for prostate cancer than for colon cancer in all but four states (where rates were equal). That tells us there is a mismatch between the scientific evidence of screening benefit and what men are actually being screened for."

Using data from a survey of almost 50,000 men conducted by the Centers for Disease Control and Prevention in all 50 states, the researchers compared the prevalence of PSA screening and colorectal cancer screening — whether men had ever been tested and whether they were up to date on screening. The study also ranks each state according to percent of men tested for both cancers as well as the states that are most up to date with their screening.

The researchers found that 75 percent of American men over 50 have had a PSA test at least once, compared to 63 percent for any colorectal cancer test, including a fecal occult blood test — the screening test with proven benefit. Among men aged 50–69, 54 percent reported an up-to-date PSA screen (within one year) and 45 percent reported up-to-date screening for colorectal cancer (within 5 years).

"The results of our study make us question whether men are aware that PSA testing has not been proven to reduce the mortality from prostate cancer," Sirovich adds. "We hope our findings enhance the conversations between physicians and their patients when a decision about screening has to be made. Men who choose to be screened for cancer should be made aware of the known benefits of colorectal cancer screening in reducing colorectal cancer mortality and the fact that PSA testing has not been shown to reduce prostate cancer mortality."

The authors speculate the reason behind the more frequent use of the PSA test is that it is easier for prostate cancer screening — it is just a simple blood test, while colon cancer screening is more involved. In addition, there has been more publicity about screening for prostate cancer than colon cancer. "Unfortunately," Sirovich notes, "much of this publicity has involved celebrities with the disease, whose public statements presume that the value of the screening is proven."

Physicians found that the men who were getting PSA tested the most were aged 70 and older, an age group that most experts agree stand to benefit the least from screening, if screening is beneficial at all. They are also at highest risk of having complications or adverse consequences of the further testing and treatment that ensues.

"We know that more men are being screened against cancer," says Sirovich. "Now we need to better inform them of which tests are most likely to be of benefit."

- Andy Nordhoff

What the study shows:

  • While 54 percent of U.S. men aged 50–69 reported being up to date on prostate cancer screening, only 45 percent reported being up to date on colorectal cancer screening.
  • Colorectal cancers are responsible for the large majority of premature deaths among the two types of cancer, accounting for 2 1/2 times as many years of potential life lost before age 75 as prostate cancer.
  • Deaths from colorectal cancer were decreased by 14 percent to 33 percent in the screening, while no valid randomized controlled trial evidence exists proving the efficacy of screening for prostate cancer.

Additional information from the Journal of the American Medical Association

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