Diana Zuckerman, PhD and Anna E. Mazzucco, PhD, Cancer Prevention and Treatment Fund
In recent years, there has been a growing concern that annual mammography screening for breast cancer starting at age 40 may do more harm than good for many women. Mammogram screening recommendations mainly give advice for women of average risk. Average risk means that there is no personal history of breast cancer and no genetic mutation that is associated with increased risk of breast cancer. As you read this article, keep in mind that screening guidelines vary depending on different levels of risk.
The U.S. Preventive Services Task Force (USPSTF) is an expert group that reviews the latest research findings and is widely used as a gold standard for determining medical treatment and screening. Prior to 2016, their guidelines recommended annual mammography screening starting at age 40. However, the guidelines for most women, updated in 2016, now recommend mammography screening once every two years starting at age 50. These USPSTF recommendations are the same as those suggested by the American College of Physicians. Women of average risk who are ages 75 or older, as well as women with a life expectancy of 10 years or less, should consider discontinuing breast cancer screening if they have no symptoms.
The American Cancer Society (ACS) has different guidelines and recommendations. As of 2021, they recommend that women at average risk of breast cancer start mammography at 45, undergo annual mammograms from ages 45 to 54, and then continue to undergo mammography every other year after that indefinitely, as long as they are in good health and expected to live at least 10 more years. Some experts disagree with this recommendation, pointing out that screening mammograms can do more harm than good, because there is no evidence that they save lives or result in less radical surgery. Experts do not recommend MRIs for screening women of average risk, but clinical studies are being done to determine whether they should be.
As guidelines change and vary from different experts, it may seem challenging to know what you should do. The goal of this article is to help you understand what recommendations are likely to be best for you.
What Is Best for You?
A key reminder: These recommendations are for screening mammograms, not diagnostic mammograms. Screening mammograms are scheduled to detect breast cancer whether or not you have a lump or other symptom. Diagnostic mammograms are scheduled after finding some possible evidence of breast cancer, such as a lump or abnormal findings from a screening mammogram. Mammograms are recommended at almost any age if a lump is found. The mammography recommendations also do not apply to all women, but are meant for women with average risk of breast cancer. Experts agree that women at especially high risk of breast cancer, such as those with mothers or sisters who had breast cancer, may want to start mammograms between the ages of 40 and 50 or in rare cases, even earlier.
The bottom line is that mammograms have the potential to help detect breast cancer earlier. However, like most medical procedures, there are risks as well as benefits. Whether to start at age 50, age 40, or earlier or later or never depends on several different factors.
For most women who are not at especially high risk of breast cancer, regular mammograms do not need to start before age 50. Or, to be cautious, a woman can get one mammogram earlier (around age 45), and then if it is normal, wait until she is 50 for her next mammogram. This is the advice that the National Center for Health Research and their Cancer Prevention and Treatment Fund have been giving since 2007.
Women at higher risk of breast cancer should not wait until they are 50 to have regular mammograms. Please remember that the age of 50 is only a guideline (not a strict rule), and only for women with no symptoms and who are not at high risk of breast cancer. If a woman finds a lump on her breast, a mammogram is still very important, regardless of her age. For a woman at high risk of breast cancer because of her family history or environmental exposures, regular screening before age 50, or even before age 40, may be a very good idea.
Who Is At Higher Risk?
One study from 2011 examined mammography for women at different ages and with different risk factors. The study’s authors concluded that each woman’s decision about mammography screening should be based on the following risk factors: age, breast density, history of breast biopsy, family history of breast cancer, and personal beliefs about the benefits and harms of screening. This study supports the USPSTF guidelines that women at an average risk of breast cancer can start screening once every two years at age 50, and that women at a higher breast cancer risk should consider screening before age 50.
Women who are carriers of the BRCA genetic mutation were previously recommended to begin yearly mammograms between ages 25-30, since this mutation puts them at much higher risk of getting breast cancer. Newer studies have found that starting yearly mammograms before age 35 has no benefit and may instead be harmful. Women end up with higher exposure to radiation from mammograms over their lifetime, which increases their chance of getting radiation-induced breast cancer that they may not have gotten otherwise.
Most women who have a mother, sister, or grandmother who had breast cancer at the age of 50 or older, or who are at high risk of breast cancer because of obesity or other reasons, may want to have regular mammograms (every two years) starting between ages 40 and 50. If their close relatives had breast cancer before age 40, women may consider mammograms even before age 40. Unfortunately, younger women tend to have denser breasts, which often look white on a mammogram. Since cancer also shows up as white, mammograms are less accurate for younger women (and other women with dense breasts). For those women, a breast MRI is likely to be more accurate than a mammogram, and they are safer than mammograms.
Breast MRIs are more expensive than mammograms, costing an average of $2,000 (compared to about $100 for a mammogram). The USPSTF says there isn’t enough information to recommend for or against MRIs. For that reason, insurance may not cover the cost. If you want insurance to pay for an MRI, you probably need to be recommended by your doctor due to being high risk. Women with dense breasts are at higher risk, especially women with mothers or sisters who had breast cancer at a young age. It is logical that they could potentially benefit from regular breast MRIs, but research is lacking to draw conclusions.
The Big Debate: Do Mammograms Save Lives?
Between 1975 and 2000, dramatic improvements in treatments for breast cancer became available. Surgery options were improved, important chemotherapy agents were discovered, and tamoxifen, a hormonal treatment for estrogen-sensitive breast cancer, came into widespread use. At the same time, mammography became more popular. In 2000, about 70% of women 40 and over reported that they had a mammogram within the previous two years. Despite changes in guidelines increasing the recommended age to 50, in 2018, about 67% of women aged 40 and over reported that they had a mammogram within the previous two years.
The result of these important advances, as well as a decrease in the use of hormone therapy for menopause, has been a dramatic decrease in the number of breast cancer deaths, even while more cases of breast cancer were being diagnosed. The five-year survival rate for breast cancer increased from 75% between 1974 and 1976, to 91% between 2005 and 2011. Death rates, on average, have been falling by 1.4% a year from 2009 to 2018. Have the survival rates improved because of mammography or because of better treatments?
This question became a full-fledged medical controversy in recent years. Two issues were at the root of the debate: 1) Was mammography simply uncovering more tiny, slow-growing abnormalities or cancers that would never have developed into a health threat even if they had never been discovered? and 2) Were we doing more harm than good by subjecting so many women to cancer treatment without knowing whether some of these breast abnormalities or very early cancers would really become dangerous? Since 2009, researchers have debated whether some tiny cancers disappear on their own without treatment. More importantly, experts agree that most ductal carcinoma in situ (DCIS) will never become an invasive breast cancer, even without treatment.
Regular screening mammography can possibly help diagnose cancer earlier, but the latest research suggests it may not have as much benefit for earlier diagnosis as expected. In March 2017, the Annals of Internal Medicine published a Danish study that examined whether regularly scheduled screening mammography can prevent the number of bigger, more advanced cancers that are difficult to treat. Dr. Karsten Juhl Jørgensen and colleagues looked at 30 years of data and compared women living in areas covered by screening programs to those in areas without the programs. Overall, mammography was not associated with fewer advanced cancers. However, in the areas with screening programs, diagnoses of non-advanced cancers increased. It is estimated that up to one third of the diagnosed breast cancer cases would never have caused noticeable health problems or death.
In 2021, a Swedish study published in the medical journal Cancer looked at data from 549,091 women, searching for breast cancers that were fatal within 10 years of being diagnosed, as well as advanced breast cancers. Data were collected on the type of breast cancer diagnosis, as well as the cause and date of death for each breast cancer case. The results showed that women who had participated in regular mammography (usually every 18-24 months) screening had a 41% reduction in their risk of dying from breast cancer within 10 years of diagnosis. When accounting for potential lead time (where an early diagnosis falsely makes it look like a patient’s surviving longer) and self-selection biases (when patients decide for themselves whether to participate in a research study), the estimate drops to a more conservative, but still statistically significant, 34% reduction in risk of dying within 10 years of diagnosis. The researchers compared women who received the same treatment, so the differences in survival are not related to any potential differences in treatment. However, keep in mind that even if women are less likely to die of breast cancer, they may die of other causes and therefore do not necessarily live longer than women who did not undergo screening mammography.
Other research indicates mammography may not save lives, except possibly for the women who have the highest risk of developing breast cancer. Researchers estimate that for 1,000 40-year-old women who have annual mammograms, two fewer women will die of breast cancer. During that time, approximately 600 of these 1000 women will have false alarms, and approximately 5 to 10 will have unnecessary surgical treatment that could be harmful to them. However, this research did not consider the benefits compared to the risks of regular mammography (every two years) after age 50. It is possible that starting less frequent mammography at 50 (and for women at high risk between the ages 40 and 50) could provide benefits that may outweigh the risks for most women. Although about 90% of worrisome findings from mammograms turn out to be false alarms — not cancer — many experts continue to believe that the overall benefits have been established for women over 50.
Having fewer women die of breast cancer does not, however, mean that fewer women die. None of the studies that evaluate the impact of mammography do so in terms of lives saved. Instead, they evaluate the number of women who die of breast cancer specifically.
What about breast self-exams? The USPSTF recommends against teaching women to do breast self-exams, because evidence suggests the risks outweigh the benefits. Breast self-exams have low accuracy, leading to women experiencing “false alarms” and increased anxiety. In the cases that breast self-exams are accurate and positive, the cancer is large enough to be obvious. The USPSTF and the American Cancer Society no longer recommend that doctors do breast exams on their patients for the same reason. Nevertheless, women should be familiar with how their breasts normally look and feel and report any changes to a doctor right away.
The Bottom Line: How Often Should You Get Mammograms?
Remember that mammograms expose women to radiation, which can increase the risk of breast cancer. Increasing the age of mammograms to age 50 for most women, and reducing the frequency to every two years could save lives because it would drastically reduce radiation exposure. Experts believe that less frequent mammograms also means a lower false alarm rate, and that means fewer unnecessary tests, anxiety, and possibly fewer unnecessary surgeries. To summarize, women of average risk, aged 50 to 74, should get a mammography screening every two years. However, as stated earlier, for women who have higher risks of breast cancer, these recommendations do not apply, and more frequent screenings may be beneficial. For women 75 or older, the benefits of mammography screening are not clear.
For more information:
U.S. Preventive Services Task Force, Breast Cancer Screening Final Recommendations, http://screeningforbreastcancer.org
For information about insurance coverage for free mammograms: http://www.hhs.gov/blog/2016/01/11/bottom-line-mammograms-are-still-covered.html
All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.
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