"We were surprised by the results," said lead author Brenda Sirovich, M.D., of the VA Outcomes Group, White River Junction, VT, VA Medical Center and the Darmouth Medical School.
"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, but this was not the case."
Sirovich speculates that the PSA test is more popular because it is just a simple blood test, while colon cancer screening is more involved. The study provides the first national population-based estimates of rates of screening with prostate-specific antigen (PSA) – the blood test for prostate cancer.
Using data from a Centers for Disease Control and Prevention survey of over 49,000 men from all 50 states, investigators found 75 percent aged 50 and older reported having undergone PSA testing at least once, and the likelihood of testing increased until age 80. Only 63 percent had undergone colorectal cancer screening.
"More men had been tested for prostate cancer than for colon cancer in all but four states (where the 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, "added Sirovich.
She and VA colleagues Lisa Schwartz, M.D. and Steven Woloshin, M.D., found that less than half the men surveyed were up-to-date on colorectal screenings. Men aged 50 to79 were 15 to 20 percent more likely to have had a PSA test in the past year than be up-to-date with colorectal screening.
Although prostate cancer is the second most lethal cancer among men, it develops so late in life that it often has no time to become a threat. In fact, the cascade of events that follow the discovery of prostate cancer -- such as invasive follow-up testing and surgery -- can be far more harmful than the cancer itself.
On the other hand, all major professional medical societies advocate colorectal cancer screening for adults aged 50 and older. Previous studies show that the fecal occult blood (FOB) test has greatly reduced the colon cancer death rate, and flexible sigmoidoscopy and colonoscopy could prove even better.
Colorectal and prostate cancer causes nearly the same number of deaths each year in the United States – 27,800 and 30,200 respectively. However, according to Sirovich, it is colorectal cancer that robs more living years from its victims, because people who die from colorectal cancer are typically younger than those dying from prostate cancer.
"The results of our study make us wonder whether men are aware that PSA testing has not been proven to reduce mortality from prostate cancer," said Sirovich.
"We know that men are being screened for cancer, but now we need to better inform them of which tests are most likely to be beneficial. We hope our findings will enhance conversations between physicians and their patients. Men who choose to be screened for cancer should be made aware of the known benefits of colorectal cancer screening and the limitations of PSA testing."
This study was funded by the Department of Veterans Affairs and a grant from the National Cancer Institute.
Journal
JAMA