A news release from the American Roentgen Ray Society (ARRS), one of the oldest radiology societies in the country, summarized a study that found “screening mammograms for women 40-49 detects more cancers compared with older age groups,” according to its headline. But is this true? The language of the news release is confusing, and at the end the authors write that there was not a significantly different amount of cancers detected in women aged 40-49 versus women aged 50-69. The release also didn’t provide a link to the study, which will be presented at the annual ARRS conference next month. Without the study, however, it is difficult to assess whether the benefits that the authors found are real.
The argument on when to get a mammogram is nothing new. It’s been a source of debate in the medical community for years, ever since the U.S. Preventive Services Task Force recommended in 2009 that routine mammograms for women with low breast cancer risk start at age 50, instead of age 40. But not everyone is on board. The American Medical Association still advocates for mammograms to begin at age 40, while the American Cancer Society has issued guidelines saying that annual mammograms should begin at age 45. The decision on when to begin screening with mammograms is an important one, as they are the gold standard for detecting breast cancer (over 200,000 women and 2,000 men are diagnosed with breast cancer each year). But it is also a personal one, and should be considered in the context of cost and individual risk, among other factors.
Costs are a huge part of the controversy on when to begin breast cancer screenings. This news release doesn’t mention the cost of mammograms, but they can be substantial. One study published in the Annals of Internal Medicine found that in terms of cost-effectiveness, it was five times more cost effective to do mammograms on women over the age of 50 than women aged 40-49. This is because while the costs of mammograms stay the same, the incidence of disease is much lower in the 40-49 age group.
The numbers in this news release were very confusing. The news release began by saying, “When compared to the screening population ages 50 and over, screening mammography in women ages 40-49 detects 19.3% additional cancers.” However by the end of the release, they wrote “the number of cancers detected in women ages 40-49 was not significantly different from women ages 50-59 or 60-69.” So which is it–did the mammograms detect more cancers or not? It left us, and likely readers, feeling unsure. It’s also not unexpected that if you test more women, you will find more cancer. But do all of these cancers need to be treated? Not all breast cancers will spread and be life-threatening. Overdiagnosis (finding an actual cancer that doesn’t need to be treated) could lead to unnecessary treatment with surgery and chemotherapy, which is obviously harmful if the cancer didn’t need to be treated.
The news release did not explain additional harms of earlier mammogram screening, of which there are several. One is radiation exposure; though mammograms involve minimal radiation, the risk of exposure still exists. The larger harm, however, is the possibility of false-positives and false-negatives. Mammograms aren’t foolproof tests; the American Cancer Society estimates that mammograms miss 1 in 5 breast cancers (false negatives). They also estimate that about half of women getting an annual mammogram over a 10-year period will have a false positive (where the screening indicates something abnormal, but in reality there is no cancer). False positives are more common in younger women, and can lead to additional tests, cost and anxiety for women when nothing is wrong. The higher rate of false positives in women ages 40-49 is one of the reasons that the mammogram age is so controversial. For the group 40-49 years of age about 3% of the callbacks resulted in an actual cancer detected while it was about 6% and 7% in the older age groups.
The news release said that the findings from this study will be presented at the 2018 ARRS Annual Meeting this April, and the study has not been published yet. From the news release it seems as though the study had a large sample size, which is good. But without the study itself we miss crucial information about the women studied, if there were any biases and study limitations, and what sort of measures the researchers used to take confounding variables into account. At this point, we only have preliminary data.
Without understanding the study methods, it’s unclear how the study sample was drawn and specifically if the sample was randomly selected.
The release veers into disease mongering with this sentence:
“When compared to the screening population ages 50 and over, screening mammography in women ages 40-49 detects 19.3% additional cancers at the expense of an overall 1.5% increase in callbacks and 0.1% in increased biopsies….”
This sentence makes it sound like the incidence of the disease is high in this age group. In fact, at age 40 the average woman has a 1.45 percent (or 1 in 68) chance of developing breast cancer over the next 10 years.
The news release did not mention anything about funding sources or conflicts of interest for the study. Just because a radiology society put out a study that proposed using more radiology procedures doesn’t mean that there was a conflict of interest; but without disclosures from the study, we can’t be sure.
The news release didn’t discuss breast MRIs or other ways of detecting cancer in younger women. While there are other procedures, such as ultrasounds, that can detect breast cancer, mammograms remain the gold standard of breast cancer screening.
Mammograms are a widely available intervention. However, like all medical care, women in rural areas far away from clinics or hospitals may have trouble accessing mammograms.
One thing that the news release didn’t mention is that this debate is not new– organizations have been going back and forth on when to recommend mammograms for almost a decade. There are compelling arguments for both sides, but this study is only one in a body of evidence that advocates for earlier mammograms. It would have been better if the news release had added some context about the mammogram debate to help readers understand why (or why not) this research was important.
No unjustifiable language.