March 18, 2003 -- While colorectal cancer screens have been shown to reduce the risk of dying from the disease, the same can't be said of the popular prostate cancer screening test. But guess which is more often given to American men?
While 75% of men report having had a prostate-specific antigen (PSA) blood test to screen for prostate cancer, only 63% have ever had any of three primary colorectal cancer detection tests, according to a new study. These include a fecal occult blood test to detect blood in the stool; a sigmoidoscopy, in which the lowest one-third of the colon is examined with a camera fixed on a flexible tube; and the more comprehensive colonoscopy, in which the entire colon and lower intestines are examined.
This finding, published in the March 19 issue of TheJournal of the American MedicalAssociation, is based on data from nearly 50,000 men at least age 40 who participated in an annual national telephone survey conducted by the CDC.
"We were surprised," says lead researcher Brenda E. Sirovich, MD, of Dartmouth Medical School and the Veterans Affair Medical Center in White Junction, Vt. "We expected to find that medical screening practices are more parallel with the evidence of benefit. But we found the reverse."
Though research is under way to investigate the real value of prostate cancer screening in reducing the rate of death from prostate cancer, there currently is no proof it helps. But experts agree that any of the three colorectal procedures can help detect colorectal cancers at earlier stages, where they are most treatable.
In her study, Sirovich notes that in three separate trials involving some 250,000 men, the death rate was reduced as much as one-third among those screened for colon cancer with a fecal occult blood test -- the most studied of the three screenings and the one recommended annually for everyone after age 50.
"Many believe that flexible sigmoidoscopy and colonoscopy will prove even more beneficial," she tells WebMD. That's because in addition to being more thorough screenings, some existing polyps can be removed during these procedures.
Sigmoidoscopy, which takes about 10 minutes and can be done in a doctor's office, examines the lowest one-third of colon -- where 60% of the cancers occur. It is recommended every five years after age 50, sometimes with a fecal blood test. Colonoscopy is an outpatient procedure done under light sedation and takes about one hour to perform, but requires bowel preparation; it can replace the two other screenings when done every 10 years starting at age 50.
A fourth test, a double contrast barium enema, is rarely done these days to detect, but not remove, large polyps. It is typically reserved for the elderly, heart patients, and others who shouldn't be sedated or can't handle either "oscopy."
So why are prostate screenings more popular?
"Colorectal cancer screening, quite simply, has not been well integrated into primary care," says Robert A. Smith, PhD, director of cancer screening for the American Cancer Society. "It's because doctors aren't pushing for it. When we ask patients why they have been screened for colorectal cancer, they'll say it's because their doctor recommended it. When you ask them why they haven't been screened, they'll say their doctors didn't recommend it. What you often see in these situations is a complete disconnection in physicians' perception of what their patients want and don't want."
Of course, there are other possible explanations: "PSA is a simple blood test and prostate cancer is foremost in mens' minds," Smith tells WebMD.
"There's more publicity on screening for prostate cancer, and a lot involves celebrities who have the disease and make public statements presuming that the value of screening is proven," says Sirovich. "There is just the message, 'Get the test,' without the science of evidence that it actually provides a benefit."
While Katie Couric is well known for promoting the benefits of screening for colon cancer -- her husband died from the disease -- Sirovich says the Today show host stands alone as its celebrity advocate. "But there are at least 10 celebrities promoting prostate cancer screenings."
Interestingly, March is National Colorectal Cancer Awareness Month.
That media attention, by Gen. Norman Schwarzkopf and other prostate cancer patients, helps remind men that this cancer is the most common one they face after lung cancer. This year, about 220,900 new cases will be diagnosed in the U.S., compared with 151,000 predicted cases of colorectal cancers detected in both sexes, reports the American Cancer Society.
However, less publicized is the similar death rate among both diseases. Prostate cancer will kill about 28,900 men in 2003, while about 28,300 men (and nearly the same number of women) are expected to die of colon cancer, and 9,400 men and 5,500 women will die from rectal and anal cancers.
One reason: Prostate cancer typically strikes at an older age and is slower to spread -- one reason for debate on the value of PSA screenings. While few argue that the test may lead to more diagnoses, some believe that treating some prostate cancers can cause more harm and provide no improvement in life expectancy or quality. And prostate cancer is often diagnosed at an older age, when other conditions are statistically more likely to cause death before the cancer.
"While there is no conclusive proof yet on the benefits of PSA, it doesn't mean there's not a growing body of very persuasive evidence to tell us that PSA testing does work," says Smith. But with that definitive proof still on the horizon and concerns over treatment, the American Cancer Society currently offers no recommendation on whether men should be screened with PSA -- instead advising them to discuss personal risk factors with their doctors.
"But there is no question you should be screened for colorectal cancer," says Smith. "And there is no question of its benefits."