1. Home>
2. Specialties>
3. General Medicine>
4. Clinical Practice Guideline Watch

Screening Mammography Recommended for Women 40 or Older

A new guideline from the Agency for Healthcare Research and Quality recommends routine mammography for women 40 and older.

The third U.S. Preventive Services Task Force (USPSTF) has been releasing new and updated guidelines during the past year (http://www.ahrq.gov/clinic/uspstfix.htm#review; Journal Watch May 15 2001; Journal Watch Nov 9 2001; and Journal Watch Feb 1 2002). This guideline is the latest in the series.

USPSTF 3 concludes each of its guidelines with a recommendation, graded as follows:

A -- The intervention is strongly recommended.

B -- The intervention is recommended.

C -- The USPSTF makes no recommendation for or against the intervention.

D -- The intervention is not routinely recommended.

I -- Evidence is insufficient to recommend for or against the intervention.

Most professional societies that comment on breast cancer screening recommend periodic mammograms for women 50 or older, but there is controversy about mammography for women who are 40 to 49. The USPSTF evaluated the effectiveness of mammography, clinical breast examination, and breast self-examination for early detection of breast cancer. Since the last USPSTF guideline on this topic was issued, longer follow-up in some randomized controlled trials has been reported. Based on a systematic review and meta-analysis (as yet unpublished) that included these data, the USPSTF has concluded that there is fair evidence that mammography at 12- to 33-month intervals reduces mortality from breast cancer in woman 40 or older. The task force recommends screening mammography, with or without clinical breast examination, every 1 to 2 years for women 40 or older. Recommendation: B

The task force reviewed 8 randomized controlled trials of mammography (in 4 of these, mammography plus clinical breast examination was evaluated) that included 11 to 20 years of follow-up. For women 50 or older, 7 trials yielded a summary relative risk for breast cancer death of 0.77, which is a significant reduction; for women aged 40 to 49, the summary RR was 0.83 (95% CI, 0.64-1.04) in 6 trials. These trials were judged to be of fair quality, but the methodologic flaws were considered unlikely to have accounted for the study results. The probability of developing breast cancer in the next 10 years is 1.5% for women aged 40 to 49, 2.8% for women aged 50 to 59, and 3.6% for women aged 60 to 69. The time until a mortality benefit appeared was longer for 40- to 49-year-old women (8 vs. 3-4 years); this delay means that most, but not all, of the benefit for these women resulted from mammograms done after age 49. No studies included women older than 74, but the task force recommendation also applies to older women because of their increased risk for breast cancer.

In no study was clinical breast examination compared with no screening, and in none of the 3 studies designed to evaluate breast self-examination was any benefit found. The task force noted, however, that these results did not exclude possible benefit from clinical breast examination or self-examination. The USPSTF concluded that there is insufficient evidence to recommend for or against routine clinical breast examination alone or routine breast self-examination. Recommendation: I

Comment: Although the task force recommended mammography screening in younger women, they pointed out that the absolute benefit is lower than that in older women because risk for breast cancer is lower in younger women. The probability that a woman aged 40 to 49 with a positive mammogram actually will have breast cancer (positive predictive value) is 2% to 4%. As a result, younger women have greater likelihood of harm and lower probability of benefit from screening than do older women. Given these data, the task force emphasized that the age at which the benefits of mammography outweigh the harms is based, in part, on patient preference, so the decision to begin screening is also subjective. At the time of publication, the full text of the original article was available at http://www.ahrq.gov/clinic/3rduspstf/breastcancer/ free of charge.

— Richard Saitz, MD, MPH

Published in Journal Watch General Medicine March 19, 2002

Citation(s):

U.S. Preventive Services Task Force. Screening for breast cancer: Recommendations and rationale. Accessed March 4, 2002, at http://www.ahrq.gov/clinic/3rduspstf/breastcancer/