A high-quality screening mammogram is still considered the best way to catch breast cancer as early as possible. But members of the medical community disagree on what age all women should start getting annual mammograms, and breast cancer screening has become an increasingly polarizing topic as a result.

Experts agree that every woman over 50 needs a mammogram at least every two years to ensure they are in good health, while those under 40 years old do not. The controversy involves women in their forties, a group that is in more of a gray area when it comes to the benefits versus the harms of regular screening. (Note that women at high risk for breast cancer, such as those with a BRCA1 or BRCA2 mutation, fall under a separate set of guidelines.)

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What harms could there be in discovering a potentially deadly disease? The one most often cited is overdiagnosis, defined as the detection of cancers that would not have otherwise caused symptoms or death in the woman's lifetime. With their growing power and resolution, imaging tools today are able to capture even the smallest hints of a tumor — some of which may end up being harmless. Overdiagnosis can lead to anxiety and possible overtreatment (e.g. radiation, chemotherapy), since there is no foolproof way to tell which cancers will or will not progress.

New guidelines issued on Tuesday by the American Cancer Society recommend raising the age when women of average risk should start getting screened -- from 40 to 45.

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In April of this year, the U.S. Preventive Services Task Force (USPSTF) — a national panel of physicians from the fields of preventive medicine and primary care — released new draft recommendations that women should begin screening every two years starting at age 50. Mammograms for women ages 40 to 49 is optional depending on their health history and preference. The USPSTF states that participation in screening for those in their forties should be a personal decision made in consultation with their doctor.

But other experts strongly believe all women in their forties should get mammograms, including Daniel Kopans, a professor of radiology at Harvard Medical School and a radiologist at Massachusetts General Hospital. We spoke to him about why 40 is a better threshold than 50 for screening, issues of overdiagnosis, and how the USPSTF decision could affect insurance coverage for mammograms:

Q: Why do some experts recommend stopping regular mammograms for women of average risk who are in their early forties?

Women and their doctors should know that the American Cancer Society has always and still does state that annual mammography screening starting at the age of 40 saves the most lives. The USPSTF acknowledges this fact, as clearly stated in its recent draft recommendations: “The USPSTF found adequate evidence that mammography screening reduces breast cancer mortality in women ages 40 to 74 years.”

This is where the USPSTF should have stopped, but its panel members — none of whom are experts in breast cancer care, by the way — decided to introduce their own biases by supposedly weighing the benefits (e.g. lives saved) against the “harms” of screening. One major “harm” cited was the anxiety that could accompany a false-positive mammogram. The panel members reasoned that reducing anxiety by reducing screening was reasonable, which would allow women to die unnecessarily.

Q: The American Cancer Society's guidelines were just released. What effect will the final USPSTF guidelines (which have not yet been released) have on women's access to breast cancer screening?

The biggest concern is that the USPSTF guidelines determine whether or not insurance will cover breast cancer screening. If the USPSTF gives screening women ages 40 to 49 a "C" rating (meaning the panel recommends practitioners offer or provide this service for selected patients depending on individual circumstances), then mammograms will not be covered for this age group. Only those women who can afford to pay will be able to participate in screening. Similarly, if the panel states that screening every two years is sufficient instead of every year, then mammograms will only be covered every two years.

There is little question that if the USPSTF advises waiting until the age of 50 for screening every two years — unless Congress intervenes — that is what insurance will cover.

Q: So should all women in their forties be getting yearly mammograms, despite the potential harms described?

The scientific evidence shows that the most lives are saved by annual mammography starting at 40 years old, and therefore women should have unencumbered access to screening starting at that age. All women should be provided with accurate information so that they — and not an inexpert panel — can make informed decisions about their health care.

A 2013 study at the Harvard teaching hospitals found that half of the women who died from breast cancer were diagnosed while in their forties. The majority of these women, around 70 percent, were not being screened. There are more than 30,000 women diagnosed with breast cancer in the U.S. each year while in their forties. Why would you encourage women to delay screening until the age of 50, and then give cancers years to grow and spread? This makes no sense.

Q: What about the suggestions to screen only high-risk women in their forties, while everyone else can wait until they hit 50?

Only a quarter of women diagnosed with breast cancer each year have any of the known risk factors, such as genetic predisposition (BRCA 1 or 2 mutation), family history of breast cancer, or increased radiation exposure. If we only screened high-risk women, 75 percent of women diagnosed with breast cancer each year would not benefit from screening. Furthermore, the randomized, controlled trials showed a benefit from screening all women and did not separate women based on risk, so that we really have no proof that screening only high risk women will save any lives.

Unfortunately, all women need to be screened starting at 40 years old. However, I will add that high-risk women may benefit from additional MRI screening.

Q: What about the issues surrounding overdiagnosis and overtreatment of breast cancer — are they largely exaggerated or should women be worried?

The arguments suggesting massive overdiagnosis — that is, when a woman is diagnosed with breast cancer that would not become a threat during her lifetime — have been completely manufactured. There is no evidence that invasive breast cancers found by mammography, if left alone, would not go on to become lethal. One of the authors of a major article published in the New England Journal of Medicine that has promulgated this misinformation has stated that his analysis was based on his best guess. Subsequent analyses have shown that the study's conclusions were completely false.

All medical care is based on “overtreatment” since we are still unable to accurately predict who will benefit with certainty from any medical intervention. Regardless, screening leads to early detection, which saves lives. Screening is not responsible for "overdiagnosis" — pathologists make the diagnosis. Screening is not responsible for “overtreatment” — oncologists decide on treatment. Women should not be deprived of life-saving screening because medical care is not perfect.

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