Over the past several decades, a growing number of young adults are being diagnosed with cancer in what some experts have called "an emerging global epidemic."
Worldwide incidence of cancer in people under 50 rose by nearly 80% from 1990 to 2019, according to the Global Burden of Disease study. Out of 29 types of cancer in the analysis, early-onset breast cancer had both the highest incidence and mortality.
"This increase is not related to changes in screening practices, given that this is an age group that was not recommended for population-based screening at the time," says Rebecca Kehm, PhD, assistant professor of epidemiology at the Mailman School of Public Health at Columbia and member of the Cancer Population Sciences Program at the Herbert Irving Comprehensive Cancer Center (HICCC).
What is driving this surge of early onset breast cancer? Researchers from the HICCC are investigating a range of potential factors, including how hormones and puberty may play a role.
Getting (and staying) physical
Rebecca Kehm, PhD
Research has long shown that regular exercise can lower the risk of breast cancer and other types of cancer. But when does physical activity make the biggest impact? A recent study by Kehm and her colleagues focused on specific "windows of time" in life to see how exercise might influence breast cancer risk. The study found that staying active during adolescence and early adulthood can significantly reduce the risk of developing breast cancer before age 40.
"The adolescent period is the time where physical activity levels dramatically decline in individuals, and then once they drop off, they remain low into adulthood," she says. "We need to think about creating opportunities for girls to be more physically active and the long-term impact that such interventions could have, even extending to reducing breast cancer risk at a population level."
The study included data from 2,502 women diagnosed with breast cancer before age 40. They self-reported their average hours per week of moderate and strenuous exercise activities or sports during adolescence (12 to 17 years) and early adulthood (25 to 34 years).
Women who were highly active during both adolescence and early adulthood had a 22% lower risk of early-onset breast cancer compared with women who were not highly active during either time period.
"Physical activity can be important for hormone regulation, so it can lower estrogen levels in individuals, which reduces risk for cancer," Kehm says. "We also know that exercise has properties for reducing chronic inflammation and oxidative stress."
The puberty puzzle
Lauren Houghton, PhD
Lauren Houghton, PhD focuses her research on how hallmarks of puberty - like the timing of the first menstrual cycle (menarche) as well as breast development - can impact the risk of early-onset breast cancer. Women who have their first period before age 12 have a 23% higher risk of developing breast cancer than those who start at 15 or later. Similarly, starting breast development earlier in life is linked to a 20% higher risk of breast cancer.
"Puberty is a critical window for when the breast is developing, and understanding the hormonal shifts happening during this period is key to understanding their connection to breast cancer," explains Houghton, assistant professor of epidemiology at the Mailman School of Public Health at Columbia and member of the Cancer Population Science Program at the HICCC. "Because breast cancer often takes years to develop, when we see cases in younger women, it speaks to the importance of the adolescence period and what happens during that time that could be driving some of these trends we're seeing."
In a recent invited commentary titled "Menstruation as the Next Vital Sign," Houghton points out that the first cohort of women in the US who started menstruation at 12 ½ years of age are the same who are now experiencing an increase in early onset breast cancer, highlighting their potential association. Additionally, those born between 2000 to 2005 are at 20% increased risk of breast cancer because they are the first cohort, on average, to reach menarche before 12 years of age. She warns that in 2033, we can expect a markedly higher incidence of early-onset breast cancer and urges clinicians to inquire about patients' menstrual health to look for warning signs of underlying risk and pathology.
Using hormones to fill the screening gap
Recently, Houghton and her colleagues investigated the possibility of using hormone profiles to detect early signs of breast cancer. After collecting urine samples of mostly premenopausal women, they measured levels of estrogen and progesterone, but also stereotypically "male" hormones known as androgens, as well as glucocorticoids, which are stress hormones. When comparing patients and controls, the results pointed to heightened glucocorticoids and androgens as being linked to an increased risk of breast cancer.
"Having a gendered view of hormones has really limited research because the fact is, women also have what we think of as male hormones, these androgens. When we look at premenopausal breast cancer, it's androgens that are more consistently associated with breast cancer risk," she says. "Now we're trying to think through ways that we can use these hormones as a biomarkers for screening for early-onset breast cancer."
