Study shows breast cancer rates are increasing in younger women

Breast cancer diagnoses have increased steadily among women under 50 over the past two decades, with more pronounced increases in recent years, according to a study led by researchers at the University of Medicine School of Medicine. Washington to St. Louis. This increase is largely due to an increase in the number of women diagnosed with estrogen receptor-positive tumors, cancerous tumors fueled by estrogen.

Although overall trends show increases, some decreases have been observed in specific tumor types and among specific groups of women. Such changes in disease rates in young women observed over time – analyzed by age, race, tumor type, tumor stage and other characteristics – may offer clues on possible prevention strategies.

The study is published on January 26 in Open JAMA Network.

“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 tumors at a later stage. advanced, when the disease is more advanced and more difficult to treat,” said lead author Adetunji. T. Toriola, MD, PhD, professor of surgery and co-leader of the Cancer Prevention and Control Program at the Siteman Cancer Center, based at Barnes-Jewish Hospital and University School of Medicine of Washington.

“This research offers a way to begin to identify the factors driving these increasing rates, with the goal of finding ways to slow or reverse them. It could also help identify young women who are at high risk of developing early breast cancer, so that we can design interventions to evaluate in clinical trials to see if we can reduce this risk.

The research team analyzed data from more than 217,000 American women diagnosed with any type of breast cancer between 2000 and 2019. In 2000, the incidence of breast cancer among women aged 20 to 49 was d ‘around 64 cases per 100,000 people.

Over the next 16 years, this rate increased slowly, increasing about 0.24% per year. By 2016, the rate had reached around 66 cases per 100,000 inhabitants. But after 2016, for reasons researchers don’t yet understand, the trend line took a sharp turn, suddenly increasing 3.76% per year. In 2019, just three years later, the rate had reached 74 cases per 100,000 inhabitants.

Another intriguing aspect of the data is that the increase in breast cancer incidence is almost entirely due to an increase in the number of estrogen receptor-positive tumors, according to Toriola, who is also a physician-scientist at the University of William H. Danforth of Washington.

These tumors have proteins on their surface that bind to estrogen, which fuels tumor growth. In fact, the incidence of estrogen receptor-negative tumors has declined over the 20 years of data analyzed in the study.

“We need to understand what drives the specific increase in estrogen receptor-positive tumors,” Toriola said. “We also hope to learn from the decline in estrogen receptor-negative tumors. If we can understand what is driving this rate down, we may be able to apply it to efforts to reduce or prevent other types of breast tumors.”

Researchers also found higher rates of breast cancer among black women, particularly among women aged 20 to 29. Black women in this age group have a 53% increased risk of breast cancer compared to white women in the same age group.

A higher risk for black women also persists between ages 30 and 39, but the increased risk is smaller, about 15% higher than for white women in the same age range. Then, from ages 40 to 49, the rate for black women drops below that of white women.

Toriola said her group is evaluating breast tumor tissue from cancer patients of different ages and races to see if there are molecular differences that could shed light on what causes cancer to grow more in young black women. Of note, Hispanic women in the study had the lowest incidence of breast cancer of any group.

The researchers also showed an increase in stage 1 and 4 tumor diagnoses, and a decrease in stage 2 and 3 tumor diagnoses. Toriola said this data suggests that improvements in screening over the past two decades, and perhaps greater awareness of family history and genetic risk factors for breast cancer, have led to earlier detection of many tumors. But it also suggests that when stage 1 tumors are missed in younger women, the tumors tend to go undetected until they reach stage 4.

Researchers also found differences in breast cancer risk by year of birth. Toriola said the most dramatic difference was an increased risk of breast cancer of more than 20% among women born in 1990 compared to women born in 1955.

“We hope this study will provide clues to prevention strategies that will be effective in younger women, particularly young black women, who are at particularly high risk of developing breast cancer before age 40.” , said Toriola.