Can Different Guidelines Make Screening Mammography More Effective?

December 22, 2020
Whitney J. Palmer

Study finds basing screening recommendations on age does not maximize the benefit – using different factors to design targeted testing would be better.

Since 2010, more women have been undergoing mammography screening beginning at age 40. But, given the ongoing conversation about whether starting to screen women at that age actually works in catching cancers and optimizing treatment efforts, it begs the question of whether there is a way to make mammography screening more effective.

The answer is yes, according to health economists at the Massachusetts Institute of Technology (MIT), but it means targeting a different group of women and not necessarily basing new screening recommendation on age alone.

“Debates over when to recommend screening are missing a key point,” said MIT economist and co-author of the study Amy Finkelstein, Ph.D., professor of economics. “There are arguments about what the costs and benefits are of screening women at a certain age, but these tend to overlook the fact that those who follow the recommendations [for early screening] differ from the rest of the population. This makes the problem more complicated. You can’t just forget human behavior and human selection when designing recommended health care practices.”

Basically, she explained, women who tend to follow the screening-mammogram-at-40 guideline tend to be healthier than other women, and they have a lower incidence of breast cancer than women who do not start screening at that age. Still, reaching more women in that age group would result in identifying more cancers, potentially at smaller, earlier, and more easily treatable stages.

Related Content: UK Study: Benefits of Breast Cancer Screening Begins at 40

What the team found in their study, published in the American Economic Review, is that designing screening recommendations around high-risk groups – rather than age-based groups – would be more effective.

According to existing insurance data, 90 percent of mammograms conducted on middle-aged women come back negative, and only 0.7 percent of tests result in truly positive cases of breast cancer. Existing studies have revealed limited benefit for the 40-to-49-year-old group, and that has been sticking point in the mammography debate. The conversation has focused more on the average impact of mammography rather than considering the possibility that women who follow the earlier screening guidelines are likely already in a lower-risk group.

To flesh out this issue, Finkelstein’s team examined screening and diagnosis data from the Health Care Cost Institute. The information came from 3.7 million women who got a mammogram between 2009 and 2011. In addition, they pulled details from the Surveillance, Epidemiology, and End Results data based from the National Cancer Institute on more than 200,000 breast cancer diagnoses recorded from 2000 to 2014.

Using a clinical model of breast cancer disease progression in the absence of treatment, they were able to approximate the overall incidence of breast cancer in the entire population, including those women who were not screened. Based on this model, they found women who start mammography screening prior to age 40 have a positive test rate of 0.84 percent (likely because they have experienced symptoms), and women who start at 40 have a 0.56 percent positive rate.

But, they also looked at a third group who is often overlooked – the women who forego screening after age 40. It can be harder to determine their breast cancer rate, but with this model, the researchers were able to estimate their risk against women who do comply with preventive screening.

“When you make age-based recommendations, it looks like the people who are most likely to follow them are the ones for whom it’s least beneficial,” Finkelstein said, “which doesn’t mean it’s not beneficial, but those are not the people you most want to target.”

So, how do you better target the patients who might benefit most from earlier screening?

Take a look at higher-risk groups, she said. Build recommendations around non-age-related factors, such as a mother’s age at first birth or her genetic markers. At the very least, she said, these findings should become part of the larger conversation about mammography, integrating choice and behavior into the process.

In addition, said Abby Ostriker, study co-author and MIT Ph.D. candidate, these results can be used to inform recommendations for other types of cancer screening.

“We studied mammograms, but there are other kinds of cancer screening that are also very important,” she said. “This concept that the average person is not necessarily the same as the person who elects to participate is, I think, very pervasive. And, getting more attention for that is hopefully going to be helpful.”

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