Chapter 1: The Rising Trend

The noticeable increase in breast cancer cases among younger women prompts an essential inquiry: What is driving this alarming trend?

From 2000 to approximately 2016, there was a gradual rise in breast cancer diagnoses for women under 50. However, an unexpected spike has since occurred.

Source: Xu et al. JAMA Network Open 2024

As a professional who regularly analyzes data, I rarely react vocally to graphs, but one particular graph compelled me to do just that. Why has there been a sudden increase in breast cancer rates among younger women?

The data in question originates from a study published in JAMA Network Open.

Source: Xu et al. JAMA Network Open 2024

Researchers from Washington University in St. Louis employed SEER registries for their analysis. The SEER database, maintained by the National Cancer Institute, represents around 27% of the U.S. population and has a robust history of providing reliable data.

Between 2000 and 2019, over 200,000 young women were diagnosed with invasive breast cancer in this dataset, and while we've acknowledged the upward trend, the critical follow-up question is, "Why?"

Fortunately, the SEER dataset offers more than just cancer diagnosis figures. It includes demographic details, hormone receptor status, cancer stage, and additional factors, which can help us hypothesize about the underlying causes.

Let's delve into a complicated aspect of this data. The recent surge in breast cancer diagnoses among younger women warrants further examination. Is this increase merely a result of the years in question — meaning more women, in general, are being diagnosed since 2016 — known as period effects?

Alternatively, is there something specific to young women, such as environmental factors, that places them at higher risk than those born in different eras? These are referred to as cohort effects.

The researchers examined both aspects and concluded that the surge is attributable to both influences.

Source: Xu et al. JAMA Network Open 2024

The rise in breast cancer among young women stems not only from a general increase over time but also from specific risks associated with those born between the late 1970s and late 1980s.

Understanding the cancer stage at diagnosis can provide further insights. Interestingly, the rise in cases is predominantly linked to stage 1 and stage 4 cancers, rather than stages 2 and 3.

Source: Xu et al. JAMA Network Open 2024

The increase in stage 1 diagnoses may indicate improved detection methods, although many women in this age group might not yet qualify for routine mammograms. Moreover, heightened awareness of genetic predispositions and family medical histories could lead younger women to seek screenings, resulting in earlier detection of cancers. Additionally, the rise in estrogen-receptor positive tumors may reflect demographic changes, such as women having fewer children or delaying childbirth.

So, what accounts for the increase in stage 4 cases? Since younger women are generally not advised to undergo routine mammograms, those who discover lumps independently are likely to be diagnosed at more advanced stages. The authors suggest that rising rates of overweight and obesity may contribute to this trend, as previous studies link higher body mass index (BMI) to later-stage breast cancer diagnoses.

Of course, various other factors could also be influencing these trends, including environmental pollutants, hormone exposure, and more. Research will continue to explore these variables. In the meantime, it’s crucial to acknowledge that the landscape of cancer is ever-evolving, necessitating ongoing adaptations in our approach to public health. Should these trends persist, national health organizations might need to reevaluate their guidelines regarding the initiation of screening mammograms for certain young women.

This first video, The Alarming Rise of Breast Cancer in Young Women, provides an in-depth look at the troubling increase in breast cancer cases among younger demographics, examining the potential causes and implications for public health.

The second video, Breast Cancer Rates Are on the Rise Among Younger Women, offers insights into the factors contributing to this concerning trend, including lifestyle changes and environmental influences.

A version of this commentary was initially published on Medscape.com.