By Otis W. Brawley, On Monday, the U.S. Preventive Services Task Force took a step backward in the fight against breast cancer. The task force announced that it would no longer recommend

routine mammograms for women between the ages of 40 and 49,   a group that accounts for about one out of six breast cancers. The recommendation is based on data that find that mammograms do reduce the risk of death in these women, but apparently not enough deaths to recommend that all women 40 to 49 should be screened.

This development has once again raised a heated public discourse on the benefits, risks and harms of breast cancer screening. This rigorous discussion is an important part of reaching clear and understandable public health guidance. But it can be messy and confusing to the public. And, in this case, it could result in fewer women getting screened and a return to the days when we caught cancers only when they were big enough to feel. That’s a step the American Cancer Society does not want to take.

Breast cancer is the leading cause of cancer death in women ages 40 to 49, with more than 4,000 deaths expected in this age group this year. The task force says routine mammography would reduce deaths by about 15 percent. With its new recommendations, the task force is essentially telling women that mammography at ages 40 to 49 saves lives — just not enough of them to recommend that all women get screened.

The panel concluded that the harms associated with mammography outweigh its benefits. When experts talk about the harms of screening, they mean things such as having additional tests to better identify what seems to be an abnormality. That usually means another mammogram and, for a small percentage of women, a biopsy to rule out breast cancer. Naturally, these false alarms can cause anxiety, but the data tell us that women know about these limitations and accept them as the price to pay for finding breast cancer early.

Studying cancer deaths among women in their 40s reveals some important trends. Death rates were dropping slightly in the 1970s, thanks to better awareness and better treatments. In 1983, the American Cancer Society began recommending that all women get screened beginning at age 40. By 1990, death rates began a steep decline that continues today. While some of that drop is due to improvements in treatment, conservative estimates are that about half is due to mammography. Without mammography, many women would not be candidates for breast-conserving therapy. You cannot treat a tumor until you find it, and we know that mammography has led to finding tumors when they’re smaller and far more treatable.

We think the task force may underestimate mammography’s lifesaving value. In 2003, an expert panel convened by the American Cancer Society conducted an extensive review of the data available then. Our panel reviewed data similar to that examined by the federal task force as well as recent and large population-based studies of modern mammography. Those studies show much stronger benefits from screening compared with the limited data examined by the task force. The task force also restricted its analysis to a certain kind of trial. While those trials are the strongest type, their use meant the panel was limited to reviewing an older body of evidence that underestimates the benefit of modern mammography.

We acknowledge that there are limitations to mammography’s effectiveness. It is notable, however, that data show the technology used today is better than that used in the studies in the task force review. More modern studies show that mammography is achieving better results than those achieved in those early experimental studies that date to the mid-1960s. We are funding a large study to further improve the accuracy of mammography.

In the meantime, the American Cancer Society continues to recommend annual screening using mammography and clinical breast examination for all women beginning at age 40. The test is far from perfect, but it’s the best way we have to find tumors early. How many lives are enough to make routine screening worth it? How many mothers, sisters, aunts, grandmothers, daughters and friends are we willing to lose to breast cancer while the debate goes on about the limitations of mammography? Turning back the clock will add up to too many lives lost, and too many women finding their tumors later, when treatment options are limited. Our medical staff and volunteer experts overwhelmingly believe the benefits of screening women ages 40 to 49 outweigh its limitations. Let’s not behave as though we lack a tool with proven benefits to women’s health.

The writer is chief medical officer of the American Cancer Society.