New guidelines from the American College of Physicians recommend that many women do not need regular mammograms until they are 50 years old. Previously, women were advised to get regular mammograms starting when they are 40 years old. Meanwhile, the American Cancer Society is still recommending mammograms for women over 40 and also recommending regular breast MRIs in addition to mammograms.

So what is best for you?

The bottom line is that annual mammograms help detect breast cancer early and improve the chances that it can be treated successfully. However, like most medical procedures, there are risks as well as benefits. Whether to start at age 50 or 40 or even earlier depends on several different factors.

For most women, who are not at especially high risk of breast cancer, regular mammograms can start at age 50. Or, the woman can get one mammogram earlier (around age 40 or 45) and then if it is normal, wait until she is 50 for her next mammogram.

However, women at higher risk of breast cancer should not wait until they are 50 to have regular mammograms. The chances of getting breast cancer increase with age, and the disease is much more likely after age 50 than before. So, from a public health perspective, annual screening mammograms do the most good after age 50. Earlier mammograms are less accurate and more likely to result in unnecessary anxiety or unnecessary biopsies. And, mammograms expose women to radiation, which can increase the risk of cancer.

Please remember that the higher age -- 50-- is only a guideline (not a strict rule) and only for screening women with no symptoms and not at high risk of breast cancer. If a woman finds a lump on her breast, a mammogram is still recommended, regardless of the woman's age. In addition, for a woman at high risk of breast cancer, because of her family history or environmental exposures, screening before age 50, or even before age 40, may be a very good idea.

Most women who have a mother, sister, or grandmother who had breast cancer at the age of 50 or older, or who are at high risk of breast cancer because of obesity or other reasons, should have regular mammograms starting at age 40. If their relatives had breast cancer at a young age, women need to consider mammograms even before age 40. Unfortunately, younger women tend to have denser breasts, which often look white on a mammogram. Since cancer also shows up as white, mammograms are less accurate for younger women (and other women with dense breasts). For those women, a breast MRI is especially likely to be more accurate than a mammogram, and they are safer than mammograms.

Breast MRIs are more expensive than mammograms, unfortunately, costing an average of $2,000 (compared to about $100 for a mammogram). So, if you want insurance to pay for an MRI, you probably need your doctor to recommend it because of your high risk. Women at high risk, especially women with mothers or sisters who had breast cancer at a young age, should try to get regular breast MRIs.

Mammograms Save Lives
Between 1975 and 2000, dramatic improvements in treatments for breast cancer became available. Surgery options were improved, important chemotherapy agents were discovered, and tamoxifen, a hormonal treatment for estrogen-sensitive breast cancer, came into widespread use. At the same time, mammography became more popular. In 2000, about 70% of women over 40 reported that they had a mammogram within the previous two years.

The result of these important advances has been a dramatic decrease in the number of breast cancer deaths, even while more cases of breast cancer were being diagnosed. The five-year survival rate for breast cancer increased from 75% between 1974 and 1976, to 88% by 1995-2000. Have the survival rates improved because of mammography or because of better treatments?

This became a full-fledged medical controversy in recent years. Two issues were at the root of the debate: 1) was mammography simply uncovering more tiny, slow-growing cancers that would never have developed into a health threat even if they had never been discovered? and 2) were we doing more harm than good by subjecting so many women to cancer treatment without knowing whether some of these very early cancers would really become dangerous? (See "Should Women Undergo Mammograms" for more details about this debate.)

A study by Berry et al and published in 2005 tackled these questions head-on. The researchers, working at seven different centers across the United States, concluded that mammograms are responsible for between 28 to 65% of the sharp drop in breast cancer deaths that occurred in the United States between 1990 and 2000. The new treatments account for the rest of the drop.

Risks and Benefits
Regular mammograms save lives. The benefits of regular mammograms after age 50 outweigh the risks for most women. It is still true that about 90% of worrisome findings from mammograms turn out to be false alarms - not cancer. Nevertheless, the overall benefits have been established, for women over 50, and for women at high risk who are over 40.

References: Berry, DA; Cronin, KA, Plevritis, SK, et al. Effect of Screening and Adjuvant Therapy on Mortality from Breast Cancer. New England Journal of Medicine, 2005, 353 (17), pages 1784-1792.

Screening Mammography for Women 40 to 49 Years of Age, available from the American College of Physicians at http://www.annals.org/cgi/content/summary/146/7/511