Less Frequent Mammograms for Older Women?

Getting a mammogram every other year, rather than every year, did not increase the risk of advanced breast cancer in women ages 50 to 74, says a study. The study looked at data from more than 900,000 women. Data were collected between 1994 and 2008. Women who got less frequent mammograms were not more likely to be diagnosed with advanced breast cancer. This was true even for women taking estrogen replacement therapy, and for women with dense breasts. In 2009, the U.S. Preventive Services Task Force said that women should have mammograms every other year starting at age 50. The American Cancer Society still recommends annual mammograms starting at age 40. The study was published in the online version of JAMA Internal Medicine. Reuters wrote about it March 18.

By Howard Lewine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Women routinely subject their breasts to the often uncomfortable exam called a mammogram. They endure because they believe it can detect breast cancer at an early stage. And they believe catching cancer early means that it will likely be easier to treat, helping to save lives.

Indeed, a mammogram does find small cancers that no woman or doctor would be able to feel. But more often than not, the worrisome spots detected turn out not to be cancers. These are called false positives. But the spots can't just be ignored. The result is more tests and worry.

Science has been trying for years to weigh the benefits of finding early breast cancers against the risks related to false positives. This has led to major debates about the pros and cons of mammograms to screen for breast cancer. Some studies suggest that this test does not live up to the hype. But most experts recommend that women have regular breast cancer screening with mammograms.

So far, the experts have primarily debated about how often to do mammograms based on age. This study also looked at other factors known to influence breast cancer risk. The researchers reviewed the records of 934,098 women who had mammograms; 11,474 of them were diagnosed with breast cancer.

Here are the key findings:

• Women with the fattiest breasts had the lowest risk of advanced breast cancer.
• Women with little fat and very dense tissue on mammography had an increased risk of breast cancer. This was especially true for women ages 40 to 49. Most women in this age range are premenopausal.
• Women that took combination hormone therapy for more than 5 years had an increased risk of breast cancer. Combination therapy means taking both estrogen and progesterone.
• Women with dense breasts who also took combination hormone therapy were at even greater risk of developing advanced breast cancer.
• Women ages 50 to 74 had no greater risk of advanced cancer if they had a mammogram once a year or once every two years.
• Women ages 40 to 49 who had breasts with normal density did not appear to have an increased risk of developing advanced breast cancer if they were screened every other year instead of yearly.
• Yearly mammograms increased the number of false positives for all women, especially those with denser breast tissue.

What Changes Can I Make Now?

Women ages 50 – 74. If women in this age group have an average risk of breast cancer, they can feel comfortable opting to have a mammogram once every 2 years.

Some women in this age group may have very dense breasts. It's uncommon in older women. But women with dense breasts might opt for screening once per year. However, they need to realize that any abnormal spot on a mammogram will likely lead to more testing and a biopsy.

Women ages 40 – 49. There is less agreement about if and how often screening mammograms should be performed in women of this age group.

Up to 15% of these women have breast dense tissue, which puts them at higher risk than other women. Having a yearly mammogram decreases their risk of advanced breast cancer. But mammograms in these women are difficult to read. Therefore, there are many false positives. And a false positive almost always leads to a biopsy.

Whatever your age, you can reduce your risk of breast cancer by:

• Maintaining a healthy body weight
• Staying physically active and exercising daily
• Eating a diet rich in fruits and vegetables
• Drinking little alcohol, or none at all

What Can I Expect Looking to the Future?

Recently, new medical evidence suggests that we may be doing cancer screening too often. For example, Pap smears to look for the early changes of cervical cancer can now be done only once every 3 years or even less often in many women. The value of general PSA blood testing to find early prostate cancer remains controversial, especially in older men.

Mammograms likely will remain a valuable screening tool. But rather than having general recommendations based on age, other more personal factors will help determine the best types of screening and how often the exams should be done.