Several large studies, including a review by the U.S. Preventive Services Task Force in 2009 and a study on the causes of death in the United Kingdom in 2013, have questioned the value of screening mammograms.
Doctors who question the value of mammograms say that while mammograms do save lives, for each breast cancer death prevented, three to four women are overdiagnosed. Overdiagnosis means either:
- a screening mammogram finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
- a screening mammogram finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated
False positive results from screening mammograms also have helped fuel the debate about the value of breast cancer screening. When a mammogram shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.
These studies and the resulting stories in the media have fueled an ongoing debate about the value of screening mammograms.
Since that time, the American Medical Association, the American College of Obstetricians and Gynecologists, the American College of Radiology, the National Cancer Institute, and the National Comprehensive Cancer Network all have issued guidelines saying that all women should be eligible for screening mammograms starting at age 40.
Now the American Cancer Society (ACS) has released updated breast cancer screening guidelines that recommend that women at average risk start regular annual screening with mammography at age 45 and move to screening every 2 years at age 55. The guidelines also say that women ages 40 to 44 should have the option to begin screening early and that women 55 and older should have the opportunity to continue screening every year if they choose.
The guidelines were published in the on Oct. 20, 2015 issue of the Journal of the American Medical Association. Read “Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update From the American Cancer Society”.
“These recommendations are made with the intent of maximizing reductions in breast cancer mortality and years of life saved while being attentive to the need to minimize harms associated with screening,” said Kevin Oeffinger, M.D., chair of the breast cancer guideline panel and a family physician at Memorial Sloan Kettering Cancer Center. “The benefits, burdens, and judgment about that balance differ depending on a woman’s age, health, values, and preferences. These recommendations recognize and reflect those differences.”
The guidelines recommend:
- All women should become familiar with the potential benefits, limitations, and harms associated with breast cancer screening.
- Women with an average risk of breast cancer should undergo regular screening mammography starting at age 45 (strong recommendation).
- Women who are 45 to 54 years should be screened annually (qualified recommendation).
- Women who are 55 and older should transition to biennial screening [screening every 2 years] or have the opportunity to continue screening annually (qualified recommendation).
- Women should have the opportunity to begin annual screening between the ages of 40 and 44 (qualified recommendation).
- Women should continue screening as long as their overall health is good and they have a life expectancy of 10 years or more (qualified recommendation).
- The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation).
A strong recommendation means that the guidelines panel agreed that the benefits of the intervention outweigh any undesirable effects that may result from screening.
A qualified recommendation means that there is clear evidence of benefit, but less certainty about the balance or benefits and harms, or about patients’ values and preferences, which could lead to different decisions about screening.
The guidelines were developed by the American Cancer Society Guideline Development Group, a panel of generalist clinicians, biostatisticians, epidemiologists, economists, and patient representatives convened by the American Cancer Society. The guideline development group commissioned a systematic review of the evidence by an independent center, the Duke University Evidence Synthesis Group, to inform the recommendations process.
It’s important to know that these new guidelines are for women at AVERAGE risk of breast cancer. According to the ACS, “average risk” means women who are not at higher risk due to known or suspected risk factors that would lead to recommending earlier initiation of screening, shorter intervals, or use of different imaging technology.
It’s also important to know that for many women risk is underestimated. The assumption that we can accurately identify 100% of the women who are at average risk of breast cancer may be a risky default position. Risk is complex, poorly understood, and it’s often inconsistently assessed over time.
For example, even the risk assessment models doctors use all the time can underestimate risk in women with a strong family history of breast cancer. The Gail model focuses on the immediate and maternal side of the family -- excluding the father’s side -- even though risk is inherited equally from both parents. Also, if there are new cases of breast or related cancers in a woman’s family, her average risk may increase, but if her medical records aren’t updated, this increased risk might be missed.
It’s also important to know that delaying detection can mean more aggressive treatments as well as lives lost. While the guidelines are concerned about the harms of unnecessary biopsies and overtreatment, the harms of a missed or late diagnosis doesn’t seem to be considered. Breastcancer.org believes that saving even one life is worth more regular screening.
Finally, these new ACS guidelines don’t take into account the improvements that 3D mammography, also called tomosynthesis, add to breast cancer screening.
“The issue for women ages 40 to 49 is that with conventional 2D mammography there are clearly too many false positives,” said Emily Conant, M.D., chief of breast imaging at the University of Pennsylvania Medical Center and member of the Breastcancer.org Professional Advisory Board. “At the same time, we can't even find some of the cancers on 2D mammography. Many of the false positives in this age group are because the mammogram is their first or ‘baseline’ with no earlier mammograms to compare it to so the radiologist can say, ‘Oh, that is the way her breasts have always been -- this is just normal for her.’
“By delaying the first screening to a later age, many of these false positives also will be delayed,” Dr. Conant continued. “We will just be shifting them to the next starting age group. Not a good answer to the problem of false positives. As to the false negatives or ‘missed cancers,’ they are often obscured by overlying breast tissue -- often dense breast tissue. This combination of too many false positives relative to the number of cancers detected with 2D mammography is clearly an issue. However, most women, when asked, would rather have some extra imaging or ultrasound rather than not have cancer detected.”
Dr. Conant explained that tomosynthesis has greatly reduced the number of false positives and increased the number of cancers detected.
“Tomosynthesis has been shown to find more of the invasive cancers, the ones that almost everyone agrees are more likely to be clinically significant since they have the potential to metastasize,” she said. “Our study at the University of Pennsylvania on tomosynthesis actually showed that the cancer detection rate went up significantly in women ages 40 to 49 while we simultaneously reduced the number of false positives.
“Cancers in younger women are known to be generally more aggressive and faster growing,” Dr. Conant added. “What we need to do is keep improving our screening techniques -- tomosynthesis does this. Let's not stop looking. Let's just look with a better technology. Let’s also continue to work together to develop better technology.”
At Breastcancer.org, we believe that a woman’s best chance for early detection requires coordination of our current screening tools:
- high-quality mammography
- clinical breast exam
- self-breast exam
To not use all three tools in women ages 40 to 45 and to do mammograms alone (without clinical or self-exam) in women older than 45 are missed opportunities for early detection.
The reality is that every woman is at risk for breast cancer, and this risk tends to increase over time. It’s important to understand and regularly update your health information related to breast cancer risk throughout your life with your doctor. To get the conversation started, here are some points to talk to your doctor about:
- family history of breast or other related cancers (ovarian, melanoma)
- any test results for abnormal genes linked to a high risk of breast cancer
- results of past breast biopsies, even if they were benign
- personal history of being treated with radiation to the face and/or chest before age 30
- breast density
- weight, if you’re overweight or obese
- level of physical activity
- any use of postmenopausal combined hormone replacement therapy (HRT)
- alcohol consumption, if you regularly drink more than 3 alcoholic beverages per week
- the amount of processed food and trans fats you eat
- your smoking history
- whether or not you had a full-term pregnancy or breastfed
Breastcancer.org stands by its recommendation that ALL women have mammograms annually starting at age 40. We also believe that monthly breast self-exam and annual physical exams by a doctor are essential parts of an overall breast cancer screening strategy. If you’re at high risk for breast cancer, you should talk to your doctor about starting annual mammograms at a younger age and consider other screening tools (such as MRI or ultrasound) to maximize the opportunity for early detection.