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• Posted January 30, 2024

Why the Rise in Breast Cancers in Younger Women?

A surge in breast cancers for women younger than 50 has puzzled medical experts, but a new study provides some new information that could help halt this trend.

The steady increase in diagnoses during the past two decades has largely been driven by breast cancers fueled by the female hormone estrogen, formally known as estrogen-receptor positive tumors, researchers report Jan. 26 in the journal JAMA Network Open.

In addition, some decreases have occurred in specific tumor types and among specific groups of women -- observations that could offer clues to possible prevention strategies.

"This research offers a way to begin identifying the factors driving these increasing rates, with the goal of finding ways to slow or reverse them,"said senior study author Dr. Adetunji Toriola, a professor of surgery with the Washington University School of Medicine in St. Louis.

"It also could help identify young women who are at high risk of developing early-onset breast cancer, so that we can design interventions to evaluate in clinical trials to see if we can lower that risk,"Toriola added in a university news release.

For the study, researchers analyzed data on more than 217,000 U.S. women diagnosed with breast cancer between 2000 and 2019.

In 2000, the breast cancer rate among women ages 20 to 49 was about 64 cases of breast cancer for every 100,000 people, researchers said.

During the next 16 years, that rate increased at a slow trudge of about 0.24% per year, reaching 66 cases per 100,000 by 2016, the data show.

But after 2016, the breast cancer trend line took a steep uphill turn, increasing at 3.76% per year.

Only three years later, in 2019, the breast cancer rate among young women had reached 74 cases per 100,000 women.

"For most women, regular breast cancer screening does not begin until at least age 40, so younger women diagnosed with breast cancer tend to have later-stage tumors, when the disease is more advanced and more difficult to treat,"Toriola noted.

Researchers found that estrogen-receptor positive tumors made up nearly the entire increase in breast cancer cases.

In fact, breast cancers that didn't involve the estrogen receptor actually declined during the two decades of study.

"We need to understand what is driving the specific increase in estrogen-receptor positive tumors,"Toriola said. "We also hope to learn from the decrease in estrogen-receptor negative tumors. If we can understand what is driving that rate down, perhaps we can apply it in efforts to reduce or prevent other breast tumor types."

Black women had higher rates of breast cancer, especially those ages 20 to 29, results show.

Black females in that age group had a 53% increased risk of breast cancer, compared to white women the same age, researchers said.

Black women ages 30 to 39 also have a higher risk, but it's just 15% greater compared to white women in the same age range, researchers said.

Then from ages 40 to 49, the rate for Black women actually dropped below that of white women, results show.

Hispanic women had the lowest rate of breast cancer of any group, researchers noted.

Toriola said the research team is evaluating breast tumor tissue from cancer patients of different ages and races to try and figure out why young Black women are at increased risk.

In other results, researchers found an increase in cancers diagnosed at stage 1 and stage 4, and a decrease in diagnoses at stages 2 and 3.

This suggests that improvements in breast cancer screening and better awareness of genetic cancer risks have led to many tumors being caught early, Toriola said.

However, it also suggests that when early-stage tumors are missed in younger women, they don't tend to be detected until they've become advanced, he said.

When a woman was born also played a role in breast cancer risk, researchers added.

There was a greater than 20% increased risk of breast cancer among women born in 1990, compared to those born in 1955, results show.

"We are hopeful this study will offer clues to prevention strategies that will be effective in younger women, especially younger Black women, who are at particularly high risk of developing breast cancer before age 40,"Toriola said.

More information

The American Cancer Society has more about breast cancer.

SOURCE: Washington University, news release, Jan. 26, 2024

What This Means For You

Younger women, particularly Black women, should be aware of their increased risk for breast cancer and make sure to get all recommended screenings.