A strong dose: Chemotherapy drugs for lung cancer patients are mixed in the pharmacy at Johns Hopkins Hospital in the US

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.

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.

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.”

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 localised, these cancers in older people are associated with less sickness and better survival chances.

Three main screening tests are in use today: faecal 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 per cent.

Hemorrhoids and other factors, however, can lead to blood in the stool, and in about 90 per cent 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 per cent 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.

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.”

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 per cent 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, as well as advancing age. Cervical cancer in older women is not a more aggressive disease and, when localised, 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 per cent to 90 per cent. 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. (NYTNS)