At what age do cancer tests offer more risk than benefit?

A column about treating a growing demographic

By — Posted Nov. 23, 2009.

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Mr. Smith is an 86-year-old who comes to your office yearly for a physical exam. During his most recent visit he expresses concern you will recommend a colonoscopy. His last one was five years earlier and a 1 mm polyp was found. He had a difficult time with the preparation, complaining of abdominal cramps and stool incontinence. He does not want another colonoscopy. What should you advise?

Case history

Mr. Smith has hypertension, stage 3 chronic renal insufficiency, moderate osteoarthritis of the hip and knee, and uses a cane. He lives with his daughter and is independent with activities of daily living. He needs help with household chores, grocery shopping and transportation.


Cancer screenings, whether they are colonoscopies, mammograms, tests for prostate cancer or cervical cancer, are recommended because of their potential for saving lives by detecting disease early. However, the potential harm from the test and subsequent investigations has to be considered in assessing the benefits of testing. For older people such as Mr. Smith, the risk-versus-benefit equation is complex. The impact of the test on the patient's health and the emotional distress of taking the test and dealing with the results need to be added to the decision-making process. Age, life expectancy and the patient's state of health should be considered in deciding whether a screening is advisable.

Colorectal cancer Colonoscopies can be particularly problematic for elderly people because the invasive procedure carries some risk and preparation can be difficult. Mr. Smith experienced stool incontinence and abdominal cramps from his screening five years earlier. The frequent and urgent trips to the bathroom that accompany bowel prep are likely to be even more difficult for Mr. Smith, who has arthritis and difficulty walking. Rushing to the bathroom could increase his risk for a fall and a possible fracture. Since Mr. Smith expressed desire not to undergo the screening, his wishes should be seriously considered.

Although routine colon cancer screening of asymptomatic men and women at average risk for the cancer is recommended beginning at age 50, there is no evidence available on when the screenings should stop. For people in the recommended population, the removal of pre-malignant colorectal polyps during colonoscopy has been demonstrated to significantly reduce the development of cancer.

Some guidelines caution against screening elderly people for colorectal cancer. The U.S. Preventive Services Task Force, for example, recommends screening with fecal occult blood testing, sigmoidoscopy or colonoscopy, beginning at age 50 and continuing until 75. The task force recommends against screening adults older than 85 since "there is moderate certainty that the benefits of screening do not outweigh the harm."

The task force also recommends against routinely screening people age 76 to 85, although it is left up to the physician to decide if considerations such as high family risk for colorectal cancer or a very healthy patient might tip the equation in favor of screening. The American Cancer Society has no recommendations on an upper age limit for CRC screening.

For Mr. Smith, it would seem appropriate to forgo the colonoscopy. Although Mr. Smith is relatively healthy, other elderly patients may have many health conditions that should be taken into account when making decisions on screenings.

Breast cancer A similar situation arises in recommending a screening mammogram for elderly women. The lifetime risk of breast cancer among women in the U.S. is one in seven, based on a life expectancy of 85 years. Most guidelines recommend mammography alone or supplemented with clinical breast exams.

In a recent revision of earlier recommendations, the USPSTF suggests women be screened for breast cancer every two years from age 50 to age 74. At age 75 the benefits of screening decline, the task force said.

Because of a shortened life span among older women, the probability of overdiagnosis and unnecessary treatment increases dramatically after about age 70 or 75, the task force said. "Overdiagnosis and unnecessary earlier treatment are important potential harms from screening women in this age group."

The American Cancer Society's position is that women in good health should get mammograms every two years, starting at age 40. "Good health" might be defined in terms of whether the woman is a candidate for treatment if a cancer is detected, the society said.

The American Geriatrics Society recommends biennial screening mammography for healthy older women until age 85.

Even though mammograms are not considered an invasive procedure, potential harms and benefits still should be considered. Frail older women may be placed in harm's way from follow-up procedures, such as a biopsy, that may result from a false-positive finding or from discovery of a clinically insignificant lesion. If a cancer is found, surgery, radiation and chemotherapy also pose risks.

Prostate cancer Screening tests for prostate cancer raise even more questions. The USPSTF concludes that current evidence is insufficient to assess the balance of benefits and harms of prostate cancer screening in men younger than 75, and recommends against screening for men older than 75.

For men with a future life expectancy of 10 years or less, the task force determined that the benefits of prostate cancer screening and treatment would range from small to none. Early detection and treatment for prostate cancer can have harmful side effects, including loss of bowel and bladder control, and there is no evidence that treatment saves the lives of elderly men. Some men with prostate cancer will never develop symptoms related to cancer.

Although the American Cancer Society does not support routine testing for prostate cancer, it does recommend that physicians discuss the potential benefits and limitations before any testing is conducted. This discussion should include an "offer for testing with the prostate-specific antigen (PSA) blood test and digital rectal exam yearly, beginning at age 50, to men who are at average risk of prostate cancer and have at least a 10-year life expectancy," the group says.

Cervical cancer All women should begin screenings for cervical cancer about three years after they start having vaginal intercourse, but no later than age 21, the cancer society recommends. Beginning at age 30, women who have had three normal Pap test results in a row may get screened every two to three years.

Women 70 or older who have had three or more normal Pap tests in a row and no abnormal results in the last 10 years may choose to stop having cervical cancer screenings.

Women who have had a total hysterectomy may also choose to forego screenings (unless the surgery was a treatment for cervical cancer or pre-cancer).

The USPSTF recommends against routine screening of women older than 65 who have had normal Pap smears and are not at high risk for cervical cancer.

The geriatric society recommends Pap smears every one to three years until age 70, then stopping if tests have been normal.

General principles that should govern a physician's approach to cancer screenings of older adults include co-morbidities, life expectancy, and cognitive and functional status. Physicians should also be aware that research on screening elderly populations is limited.

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Key considerations: To screen or not to screen

Although the starting ages for most cancer screening tests have been determined, when to stop is less certain. Caution should be applied before recommending that older patients receive the following:

  • Colonoscopy -- the invasive test carries some risk, and preparation can be difficult.
  • Mammogram -- frail, older women may not be able to tolerate follow-up biopsies for possible breast cancer.
  • Prostate-specific antigen blood tests -- prostate cancer treatment can include loss of bladder or bowel control.
  • Pap tests -- most guidelines recommend halting routine screening for cervical cancer at age 65 or 70 if previous tests have been normal.

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