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Debating Cancer Screening: Too Old to Test?
By
Jane E. Brody
November 15, 2005
Stuart Bradford
When is a person too old to benefit from cancer screening tests? The answer, experts say, depends less on age than on the type of cancer, the test and individual characteristics of the person to be screened.
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It would seem logical that screening for cancers in their earliest, most curable stages would benefit anyone who might develop the cancers in question. But while the lives of some people over 65 or 70 could be saved by screening, for others the potential for harm associated with screening could outweigh the benefits.
All screening tests have risks, and experts suggest that these possible hazards, as well as the known benefits of screening, should be taken into account when deciding whether to undergo periodic screening late in life. Furthermore, the experts say, the benefits and risks of testing should be discussed with patients beforehand.
Since such discussions are problematic in the hurry-up climate of today's medical care, prospective older candidates for cancer screening would be wise to consider the issues on their own.
Screening is meant to be used for healthy people - those with no cancer symptoms. Its main benefit is its ability to reduce deaths by finding and treating early cancers that most likely would be lethal in a patient's remaining years.
Knowing the Risks
The possible risks of screening include complications of the tests themselves or with follow-up exams when screening finds something suspicious that turns out not to be cancer; detection and treatment of a cancer that would never have become a problem in a patient's lifetime; and emotional distress even after an initial positive finding turns out to be negative.
In a recent issue of The American Journal of Medicine, evidence for the pros and cons of screening older people for cancers of the colon and rectum, breast and cervix was reviewed by Dr. Louise C. Walter of the University of California, San Francisco, and her co-authors.
These experts considered only medical issues, not the costs of tests and treatment. They emphasized that "decisions about screening for cancer in older persons require weighing potential benefits and harms for each person rather than relying on arbitrary age cutoffs."
They also said that "older patients who would decline follow-up or treatment should not be screened." And, for those bothered by the discomfort and risks of screening, "the decrease in the quality of life in the present may outweigh the small chance of future benefit."
Colorectal Cancer
Cancers of the colon and rectum are more common as people age, and they are no less aggressive or less responsive to treatment than comparable cancers in younger people. When treated while localized, these cancers in older people are associated with less sickness and better survival chances.
Three main screening tests are in use today: fecal occult blood testing of stool samples; sigmoidoscopy, the use of a scope to examine the left half of the colon; and colonoscopy, the use of a flexible scope to examine the entire colon.
Occult blood tests are noninvasive and have been shown to reduce deaths from colorectal cancer in people 70 to 80 by about 15 percent. Hemorrhoids and other factors, however, can lead to blood in the stool, and in about 90 percent of cases in which the test is positive, follow-up testing, usually with colonoscopy, finds no cancer.
In patients 45 to 91, sigmoidoscopy has been shown to reduce deaths by 59 percent from cancers in reach of the scope. But older people have an increased incidence of cancers on the right side of the colon not seen through this scope.
Colonoscopy, the most sensitive of tests, is also the most involved and costly and the most likely to cause serious complications, especially in older people. Major complications, which in one study afflicted 3 patients in 1,000 among men 70 to 75, included perforation of the colon, bleeding, stroke, heart attack and blood clots.
Colorectal cancers start in adenomatous polyps, which can be found in as many as a third of older people. Fewer than 10 percent of these polyps progress to cancer within a decade. Thus, the experts concluded, "patients who have a life expectancy less than five years are more likely to be harmed from screening than to benefit."
They suggested that in addition to age and life expectancy, the decision to screen an older person for colorectal cancer should be based on factors that increase the likelihood of developing cancer, like a history of inflammatory bowel disease or previous multiple or large adenomas, as well as factors that increase the risk of complications from screening or treatment, like the presence of cardiopulmonary disease.
Breast Cancer
Breast cancer is more common in older women, but it tends to be a slower growing, less aggressive disease. It is also easier to find by mammography because the breast tissue of older women is less dense. While all well-designed studies done in women 50 to 69 found a protective effect of mammographic screening, only one such trial in eight included women over 70.
This study, done in Sweden, did not show a significant reduction in breast cancer deaths among women 70 to 74 who had two routine mammograms. In the first round of screening, 88 percent of the women with positive mammogram findings turned out not to have cancer on follow-up tests, which included breast biopsies.
The experts suggested that the decision to continue screening after 70 consider factors like the presence of a family history of breast cancer and a longer duration of exposure to estrogen (natural and in medication), as well as advancing age. They said, however, that women with other serious diseases and life expectancies of less than five years were not likely to gain from screening.
Cervical Cancer
Cervical cancer in older women is not a more aggressive disease and, when localized, it responds well to treatment. By now, every woman should know that Pap smears save lives. They can reduce the incidence of invasive cervical cancer by 60 percent to 90 percent. Yet few screening studies have included older women.
According to an analysis of Medicare claims, about 39 of 1,000 older women would need at least one follow-up procedure within eight months of having a Pap smear. These procedures range from in-office tests to surgical excisions and include colposcopy, endometrial biopsy, D and C, and cone biopsy, all with certain risks.
Another problem involves trying to determine which cervical abnormalities are likely to progress to cancer, since most resolve on their own without any treatment.
In addition, changes in the anatomy of older women can make it harder to get an accurate reading from a Pap smear. After menopause, there is an increased risk of inflammation that can mimic cancerous cell changes. The experts suggest that Pap smears should be done in women over 70 who have not been previously screened, but that women who have had repeated normal Pap smears can stop screening at age 65 or 70, as can women with a short life expectancy and those who have had a total hysterectomy.
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