A new study from the Washington University School of Medicine in St. Louis, Missouri ,has found the number of breast cancer diagnoses in women under age 50 has increasingly risen over the past 20 years. Specifically, the research team found the increase to be primarily caused by an increase in estrogen-receptor positive tumors.
The study was conducted by analyzing data between 2000 and 2019 from over 217,000 women in the United States who were diagnosed with any type of breast cancer. In 2000, the rate of breast cancer among women ages 20 to 49 was 64 cases per 100,000 people. In 2016, the rate increased to 66 cases per 100,000 patients. Three years later in 2019, the rate jumped to 74 cases per 100,000 people.
The research team discovered even higher rates of breast cancer among young Black women compared to White women of the same age. Black women aged 20 to 29 are 53 percent more likely to have breast cancer, and Black women aged 30 to 39 are 15 percent more likely than White women to receive a breast cancer diagnosis. However, for the 40 to 49 age group, the rate of Black women with breast cancer is less than that of White women. Hispanic women were found to have the lowest rate of breast cancer among all age groups.
The researchers’ analysis also uncovered an increase in stage 1 and stage 4 tumors among women under 50, but a decrease in stage 2 and stage 3 tumors. This suggests there have been improvements in breast cancer screening methods, therefore catching stage 1 tumors early enough to provide treatment and prevent the cancer from progressing further. However, the data also suggests that if a stage 1 tumor is missed in young women, it may not be found until stage 4.
“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,” says Adentunji T. Toriola, senior author of the study and professor of surgery at the Washington University School of Medicine.
The next step for Dr. Toriola and his team will be to analyze tissue from breast tumors to evaluate if there are molecular differences in tumors of women of different ages and races.
“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,” says Dr. Toriola. “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.”