Dear Dr. Hollmann,
I heard about the new guidelines for mammograms—that screening should start at age 50 instead of 40—and I'm worried about going those extra 10 years without a screening. Why is this change being made? I thought that having more screenings would be better.

The new mammogram guidelines you mention come from the U.S. Preventative Services Task Force (USPSTF), which is arguably the most respected authority on preventive medicine. The USPSTF makes a recommendation for or against a practice based upon available evidence or science. Following its most recent examination of the available data, the USPSTF determined that there's very little benefit gained by starting screening at age 40 instead of at age 50, and that the risk of harm is greater for women in their 40s than for older women. So they recommended against routine mammography screening of women aged 40 to 49.

It's important to note that the USPSTF also says that the decision to start regular screening before age 50 should be an individual one. It should take into account your values regarding specific benefits and harms, as well as your family history and general health. When mammography screening is used, the USPSTF recommends that it be performed every two years. Getting a mammogram every year compared to every two years results in almost no better outcomes and poses greater risks.

The reason why there are new guidelines is because the USPSTF is doing exactly what should be done—evaluating the best and newest information using the best methods of analysis. These guidelines are for you and your doctor to use when deciding what's right for you. The odds are very small that waiting would be an issue if you don't have a higher-than-average risk for breast cancer. But, if you are not worried much about any harm and are concerned only with the small potential for benefit, you may wish to get the screening. Below is more information that may help as you talk about this decision with your doctor.

Looking at the facts
Overall, the primary benefit of mammography is clear: It reduces deaths. No controversy there. Mammograms have been a big reason why the death rate from breast cancer has gone down 2 to 3 percent every year for the last decade. The question is: At what age do the benefits of a mammogram outweigh the possible risks? Remember, breast cancer is much rarer in younger women than older women. Statistics help put this into perspective:

• One woman in 69 gets breast cancer in her 40s as compared to 1 in 42 in her 50s and 1 in 27 in her 60s.
• It's estimated that 1,904 women must get annual mammograms throughout their 40s to prevent one death. In comparison, 1,339 women must be screened throughout their 50s to prevent one death, and 377 women must be screened throughout their 60s.
• Women in their 40s are 60 percent more likely to experience harm from mammograms than women in their 50s.

Considering the risks
Minor harm is actually common in mammography. Sometimes the results prompt another imaging study to be ordered (possibly increasing exposure to radiation) or a biopsy to be done unnecessarily (increasing the risk of infection or other complications). For women aged 40 to 49, false positive results on a mammogram are more common than among older women. On the other end of the spectrum, a mammogram can lead to treatment like a mastectomy for an abnormality that would never result in the patient's death. This is because mammography detects a type of tumor that we are unsure will develop into a lethal cancer, but is often treated as if it will, to be cautious.

Then, there is also the economic trade-off that must be considered. All those mammograms that may help only a few, but possibly harm many, add to the cost of care and drain resources that could be used on care proven to be more effective.

I hope this information helps as you and your doctor decide on mammogram screening. I'm glad you wrote in, because I think many women have the same questions and concerns as you.