Last week, I took my family to visit my parents in Michigan. Surrounded by the crisp reds, oranges, and ambers of the autumn leaves, a light breeze on a crystal clear blue sky day, drinking hot apple cider, as my young kids played in a pumpkin patch with their grandfather, I was talking with my mother. She had just finished a water aerobics class and post-workout lunch with her friends. After telling them that I was visiting for the week, and what I do for a living, they were filled with questions regarding all of the confusing information about screening mammograms.
“Why are there so many guidelines? Can’t anybody agree?” she asks me. She was referring to the fact that there are three major organizations that each recommend different guidelines for screening mammography. The SBI / ACR recommends screening at 40 every year regardless of risk factors. The USPSTF states that women can wait until 50 and receive it every other year instead of yearly, and women 40-49 should discuss with their doctor to determine if mammography is right for them. And the American Cancer Society has a hybrid guideline, stating women should start screening at 45 and receive it every year until 55, and then switch to every other year. Wow. No wonder my mother and her water aerobics class are so confused!
In the Information Age, and with access to the internet, the old model of the doctor telling the patient exactly what to do without asking for the patient’s input is outdated. Hence, many of the guidelines emphasize that screening decisions should be made after a discussion between the patient with her healthcare provider. I tried to explain that all of the guidelines actually agree on certain points. But they differ on where they draw the line of benefits versus risks in terms of making routine recommendations.
One of the most important points where the guidelines all agree is that MAMMOGRAMS WORK and that MAMMOGRAMS SAVE LIVES. If you read their full in depth scientific reports, they all agree –“Yearly screening mammography starting at age 40 saves the most lives”.
It all comes down to where the individual guidelines place the proven benefit of saving more lives versus the risks of mammography– mainly the risks of false positives and over-diagnosis or overtreatment of cancers that may not actually be harmful. The good news is that no one is really worried about radiation risks using today’s mammography technology.
Breast cancer becomes more common as women age, so some guidelines place emphasis on screening starting at 50, leaving the decade of women aged 40-49 to the individual woman’s decision after discussion with her healthcare provider. Nevertheless, it is important to know that 1 in 6 women diagnosed with breast cancer are diagnosed in their 40’s, and 75% of those cancers are diagnosed in women with no significant family history or special risk factors.
None of the guidelines recommend against screening women in their 40’s. They all acknowledge screening women 40-49 saves more lives. Some just don’t routinely recommend it as a blanket guideline (and they all make sure to include a statement that a woman should be able to receive screening her 40’s regardless of her risk, even every year if she chooses).
Some guidelines stress the risks of anxiety and unnecessary treatment associated with a “false positive” exam as a reason to not issue a blanket recommendation for screening all women every year from age 40 on. The term “false positive” means that the initial screening mammogram was called abnormal, which happens for about 1 in 10 women. My mother, in fact, was called back for additional tests a few years ago, for the first time, which, of course led to anxiety and worry as she waited for the additional tests and then the results. The more mammograms a woman has over her life, the more likely she is, from a pure probability standpoint, to have a study called abnormal at some point (even if she is normal and doesn’t have cancer). Therefore, some guidelines emphasize this risk, and say it is ok to receive mammography less often (every other year instead of every year), or that it is ok to decide to wait until age 50 to screen instead of starting at age 40. However, skipping to every other year instead of yearly mammograms will mean that some of the lives that could be saved by screening are lost. And, for the large majority of women who are called back for an abnormal mammogram, they simply need extra mammographic pictures or perhaps an ultrasound before either being cleared completely or being recommended for a follow-up test in a few months. Only about 1-2 in 100 women coming for screening will end up needing a small procedure called a needle biopsy, which is performed using local numbing medication and doesn’t leave scarring in most cases (my mother actually ended up requiring a biopsy, and thank goodness, ended up not having cancer).
The other main risk discussed by most guidelines is the risk of over-diagnosis. Over-diagnosis refers to a cancer that is diagnosed from the mammogram that would have never have grown or spread in a way that would prove fatal to the patient if it had been left alone. The easiest way to think about this is imagining finding a small 2mm slowly growing cancer in a 100 year old woman, where the patient may die from other reasons besides the cancer. However, the true amount of over-diagnosis, based on autopsy studies of invasive breast cancer, is approximately only 1 in 100 cancers. More importantly, at present, science does not have the ability to determine which cancers may confidently be left alone and followed, versus which need standard treatment. Additionally, the frequency or age of starting screening mammography does not affect the rates of over-diagnosis and so this risk should not affect which screening guideline to follow.
Mammograms are far from a perfect test! Some cancers hide – even on the best performed and most expertly interpreted mammogram. This occurs more commonly in women with dense breasts, but can occur in any woman. Any focal symptom or lump should always be brought to the attention of the provider even if a woman has had a recent normal mammogram. Mammograms do use X-ray, which is a source of radiation, and this fact frightens some women. I reassure my mother that in today’s world, the amount of radiation is tiny, and in women of screening age, who already have developed breasts (as opposed to teenagers, for example), the dose of a mammogram is essentially nothing to worry about. If she is willing to fly on an airplane roundtrip from Michigan to visit my sister in California without being scared of the exposure to radiation, she should similarly be able to obtain a yearly screening mammogram.
Most women, when aware of these facts, will choose to start screening every year beginning at age 40. A woman should always discuss her health care decisions with her provider, and of course, should feel free to choose what course of action is the most appropriate for her. But, these facts need to be conveyed to all women when they decide which guidelines they will follow. If a woman doesn’t have all of the information, she isn’t able to make an informed decision!
Phoebe Freer is an associate professor of radiology at the Huntsman Cancer Institute at the University of Utah.
This blog post was originally published October 25, 2017