The Alarming Rise of Breast Cancer in Young Women

A dramatic increase leads to a simple question: Why?

F. Perry Wilson, MD MSCE

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From the year 2000 until around 2016, the incidence of breast cancer among young women — those under age 50, rose steadily, if slowly. And then, this happened.

Source: Xu et al. JAMA Network Open 2024

I look at a lot of graphs in my line of work, and it’s not too often that one actually makes me say “what the hell” out loud. But this one did. Why are young women all of a sudden more likely to get breast cancer?

The graph comes from this paper, appearing in JAMA Network Open.

Source: Xu et al. JAMA Network Open 2024

Researchers from Washington University in St. Louis utilized SEER registries to conduct their analyses. SEER is a public database from the National Cancer Institute with coverage of 27% of the US population, and a long-track record of statistical backbone to translate the data from SEER to numbers that are representative of the population at large.

From 2000 to 2019, more than 200,000 young women were diagnosed with primary invasive breast cancer in the dataset, and I’ve already given you the top-line results. Of course, when you see a graph like this the next question really needs to be “why”?

Fortunately, the SEER dataset contains a lot more information than simply whether someone was diagnosed with cancer. In the case of breast cancer, there is information about the patient’s demographics, the hormone status of the cancer, the stage, and so on. Using those additional data points can help the authors, and us, start to formulate some hypotheses as to what is happening here.

Let’s start with something a bit tricky about this kind of data. We see an uptick in new breast cancer diagnoses among young women in recent years. We need to tease that uptick apart a bit. It could be that it is the YEAR that is the key factor here — in other words, is it simply that more women are getting breast cancer since 2016 and so more young women are getting…

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F. Perry Wilson, MD MSCE

Medicine, science, statistics. Associate Professor of Medicine and Public Health at Yale. New book “How Medicine Works and When it Doesn’t” available now.