WASHINGTON (AP) â€” The advice sounds unequivocal: Get a cancer test, it could save your life. Indeed, Pap smears, mammograms and other cancer screenings do save thousands of lives by detecting cancer early enough to treat, even cure.
But amid the push to get more people tested is a tricky question: When are you old enough to quit routine cancer screening?
It's such a murky issue that most cancer guidelines don't even mention it.
``It hasn't gotten that much attention,'' says Dr. William C. Black of Dartmouth Medical School, who analyzed federal health statistics to conclude the life-saving benefits of cancer screening fall to a startling low around age 75 and continue dropping with each birthday.
``The small benefit of screening in the elderly may be outweighed by the harms: anxiety, additional testing and unnecessary treatment.''
It's a tough issue, and one growing in importance as the population ages, says Dr. Robert A. Smith of the American Cancer Society, which hasn't set upper age limits.
``Any way that we can make cancer screening more rational and still ensure the best outcome for the majority of individuals at risk is worth pursuing.''
Cancer organizations generally agree on when screening starts: Pap smears to detect cervical cancer begin around age 18, and mammograms to spot breast cancer start at 40. Colon cancer tests start around 50, as do PSA or ``prostate specific antigen'' tests. People are urged to start screening sooner if cancer runs in the family or they have other high risks.
Left unanswered is when people become too old to benefit.
Obviously the very sick skip the tests. But many elderly people are active and healthy. The average 75-year-old has about 12 years of potential life left; some will hit 100.
The risk of getting cancer increases with age. But so does the risk of other killers; the elderly are most likely to die of heart disease.
At the same time, screening tests are becoming better, able to detect the very tiniest tumors â€” ones that may never grow fast enough to truly threaten an elderly person. Yet treating those tumors can cause serious side effects.
Black used mortality statistics to analyze life expectancy of people who undergo breast, cervical and colon cancer screening.
Giving up mammograms or the fecal occult blood test for colon cancer would cost the average 75-year-old only nine days of life, Black reported in last month's journal Effective Clinical Practice. Quitting at age 80 cost five days of life.
The average woman who gives up Pap smears at age 75 would lose three days.
In comparison, 50-year-olds getting mammograms live on average 43 days longer than those who skip the tests, Black reported.
Remember those numbers average the whole population â€” the vast majority of people screened get the good news that they don't have cancer, thus diluting the overall impact of tests that can save individuals' lives. Instead, the important finding is the dramatic age difference that shows the tests' importance wanes with time, Black stressed.
It's not the first study to cast such doubt. University of California, San Francisco, researchers have argued there's no evidence to recommend continued mammograms for most women 70 and older, yet one study found 50,000 women ages 85 and older still get regular mammograms. It's not just a breast cancer issue â€” whether to treat prostate cancer in very old men is a huge controversy.
The cancer society's Smith cautions against quitting screening just because you reach a certain age, saying healthy elderly people in particular can benefit.
But Black urges elderly Americans to thoroughly question their doctors: Will taking this test help me live longer, given my medical history? Are there signs I'm a good candidate to skip a certain test? For example, reaching 65 or 70 without catching the human papillomavirus that causes most cervical cancer might make skipping Pap smears an easy choice.
Make an informed decision, understanding that screening may require more tests or biopsies to separate cancer from a benign tumor, and that some tumors may never prove lifethreatening, Black says.
He acknowledges he's raising a controversial issue. ``I'm not looking for trouble, I'm just trying to talk straight.''
EDITOR'S NOTE â€” Lauran Neergaard covers health and medical issues for The Associated Press in Washington.