(The Hill) — Vanessa Chapoy had just turned 24 when she felt the lump in her breast. It was “huge,” she remembers, “like the size of a walnut, or a big marble.” She went to the first in a series of doctors that night to have it checked out. Two and a half weeks later, she was diagnosed with breast cancer. Stage two, she would learn.

“And my whole world flipped upside down,” Chapoy says.

She entered a gauntlet of treatments: a lumpectomy to cut out the tumor and a portion of surrounding breast tissue, fertility treatments so she could freeze her eggs, five months of chemotherapy and then a double mastectomy to remove both of her breasts. 

Three years on, she’s still undergoing hormone therapy — an experience she likens to “early menopause” — and occasionally suffering from “chemo brain,” a form of brain fog resulting from chemotherapy that she says makes it more difficult for her to complete tasks or remember certain things.

“I don’t understand how this could happen,” she recalls telling a nurse at the beginning of it all. “I’m so young.”

Cancer, after all, most often strikes late in life. In the United States, nearly 60 percent of patients are 65 or older when they’re diagnosed.

But stories like Chapoy’s are becoming more common. In recent decades, cancer rates have been climbing among people under 50, the typical cut-off for when cancer is considered “early-onset.”

This “early-onset cancer epidemic,” as one recent study published in Nature Reviews Clinical Oncology dubbed it, comprises a surge in the incidence of over a dozen different cancers in younger people since the 1990s in countries around the world.

In the U.S., the rate of early-onset cases rose by almost 18 percent between 2000 and 2019, even as cancer declined slightly in older adults, according to data from the National Cancer Institute (NCI). Among Americans between 15 and 39 years old, an age group cancer researchers refer to as adolescents and young adults (AYAs), the surge was more pronounced still, topping 20 percent.

That increase has spanned genders, races and organs. It has stormed through young people’s blood and bone marrow, launched assaults on their gastrointestinal tracts, quartered itself in their reproductive organs. The incidence of breast cancer in Americans aged 15 to 39 rose more than 17 percent over the 19-year period. Myeloma rates spiked by over 30 percent. Colorectal cancer, by nearly 45 percent.

Why? Cancer researchers aren’t entirely sure.

The rising rates are “probably partially attributable to increasing uptake of screening and early detection” in certain cancer types, especially thyroid cancer and prostate cancer, the authors of the Nature study noted.

Archie Bleyer, a clinical research professor at the Knight Cancer Institute of the Oregon Health & Science University, says the surge in cases of thyroid cancer, as well as kidney cancer, is at least partly a result of “overdiagnosis” due to increased screenings, both for cancer and for other health concerns. The screenings have detected tumors and masses in those organs that “look like cancer, so they’ve got to call it carcinoma,” he explains. But they “would never have been a problem if they were never picked up,” because they typically wouldn’t spread or progress. 

So “in some ways, it’s a false increase,” Bleyer says. 

The surge in rates goes beyond what can be accounted for by increased screenings, however. Researchers hypothesize a slew of environmental and lifestyle changes since the mid-20th century have also driven a real rise in cases by increasing exposure to risk factors early in life.

The main suspect researchers point to is obesity, which has climbed steadily since the 1960s and become more common in childhood and adolescence. Many of the cancers rising among younger people have been tied to obesity, including breast cancer and uterine cancer, as well as colorectal cancer and several others impacting the gastrointestinal tract.

The increases in obesity-related cancers have been more “dramatic” than those among other types, suggesting obesity is a “big contributor” to the spike in early-onset cases, says Tomotaka Ugai, an instructor at Harvard Medical School and Brigham and Women’s Hospital and the lead author of the Nature study. 

Beyond obesity itself, researchers believe a number of related factors could be involved: Westernized diets, sugar-sweetened beverages, red and processed meat, sedentary lifestyles, a decline in physical activity, metabolic conditions like type 2 diabetes.

And the list of suspects goes on. Bleyer says the increased use of diagnostic imaging like CT scans and X rays, which expose patients to low levels of carcinogenic radiation, could be contributing, especially for cancers impacting the blood and bone marrow. When it comes to the uptick in testicular cancer, meanwhile, he says rising cannabis use is likely the leading culprit. 

People growing taller could also be a risk factor for several cancer types, he says. Ugai tells me there’s speculation changes in our sleep patterns could be involved, though evidence is “quite limited.” Marios Giannakis, a medical oncologist and researcher at the Dana-Farber Gastrointestinal Cancer Center, says changes in the microbiome — the community of microorganisms that populate the body — have been “implicated” in the increase in early-onset colorectal cancer. These changes can result from diet, lifestyle factors or even surgical procedures like C-sections.

Giannakis stresses that more research is needed to understand what’s behind the rising rates, including long-term prospective cohort studies that follow participants over extended periods of time. 

“Finding out the why could be very relevant for prevention,” Giannakis says.

But as research continues, over 85,000 American adolescents and young adults are now being diagnosed with cancer each year. In 2020, Chapoy was one of the unlucky thousands. Two years later, I was. 

I went to the dermatologist for the first time in my life in August. Within twenty minutes of stepping into the exam room, I’d had a suspicious mole cut out of my forearm. I learned days later that I’d had melanoma, the deadliest form of skin cancer. I was 27.

My cancer was caught early and easily removed; a month after I first went to the dermatologist, all that remained of it was an inch-and-a-half-long scar and some haunting what-ifs. But that’s not the case for many adolescent and young adult patients. They’re often diagnosed at a more advanced stage, when cancer has already had time to grow and spread in the body. There are several reasons for that: They’re less likely to regularly visit the doctor than other patients. They’re more likely to be uninsured. And because cancer is relatively rare in the age group, it’s usually not top of mind for either doctors or patients as a possible explanation for symptoms. 

When Chapoy went to urgent care the night she found the lump in her breast, she said she was told “it’s nothing to worry about. You’re probably ovulating.”

“It was a struggle getting the doctors to take me seriously at first,” she says. “If I had just listened to that first doctor, I wouldn’t be here.”

Despite the often late diagnoses, adolescents and young adults are more likely to survive their initial cancer diagnosis than older adults: More than 85 percent live to see the five-year mark, compared to 74 percent of 40- to 64-year-olds and fewer than 62 percent of those aged 65 and older.

But Chun Chao, a cancer epidemiologist with the Kaiser Permanente Southern California Department of Research & Evaluation, emphasizes that “the challenge for cancer survivors doesn’t stop when they complete their treatment.” 

Cancer can recur or progress. And young survivors also face a heightened threat of developing a second cancer or an array of other medical conditions, Chao says, including “cardiovascular diseases, metabolic disorders, endocrine conditions, pulmonary diseases, liver disease, renal failure and musculoskeletal conditions.” In addition to those physical ailments, she notes survivors have an increased risk of severe depression or anxiety.

And the timing presents a unique set of challenges and disruptions to adolescent and young adult patients that extend beyond their health.

“They are at a transitional stage in life,” Chao says. “If you think about it, this is the age when people are trying to establish their independence. Some people are finishing up their education. People are trying to get their first job, just start to establish their career. And people are starting new families and starting to have kids. So at this particular age, having a cancer diagnosis can be a huge disruption to these goals.”

After Tatyana Ridgeway was diagnosed with stage one breast cancer when she was 26, she stepped away from work as she went through treatment: four cycles of chemotherapy and then proton radiation. Like Chapoy, she also underwent fertility treatments, as chemotherapy can negatively impact fertility and even cause early menopause.

The experience “shattered my idea of what parenthood was like. It shattered my idea of what your 20s are supposed to look like,” she says. “My ideas, my beliefs of — by this age, we’re going to start trying for a kid, and then by this age, we want to be done — all of those plans fell off the shelf and just broke.”

She was able to preserve some embryos. But it was costly, she says. Her IVF treatments were covered by insurance, but she had to take out a loan to cover the cost of cryopreservation. 

Her other treatments weren’t cheap either. Each of her four cycles of chemotherapy cost $15,000, and her proton radiation altogether cost over $100,000. “That’s without insurance,” she says. 

Chao notes that a “high proportion” of young adult survivors report financial hardships related to cancer, including “having to borrow money, going into debt or even filing for bankruptcy.”

Ridgeway, who is Black, says she also looked into cold cap therapy, which can help reduce hair loss brought on by chemotherapy. But she learned no one with her hair texture — “textured, curly, kinky hair” — had been included in trials for the therapy, and no one her age had been studied, either.

“There’s a lack of research specific to this age group,” says Alison Silberman, the CEO of Stupid Cancer, a nonprofit that advocates for adolescents and young adults impacted by the disease. She describes the demographic as an “underserved and underrepresented population” when it comes to cancer.

“There has been a growing awareness” over the last couple decades amid the increase in cases, she says. But it “depends on where you are. A lot of the larger academic institutions are well versed in AYA needs and challenges and differences. That doesn’t happen as much in the smaller community settings.” And she notes while there’s “slightly more academic research,” there may still not be “as much clinical research.” 

“I think there’s still a lot of work to be done,” she says.

Researchers stress the importance of further raising awareness about cancer in the age group — among both young people themselves and their doctors — and studying their cases so treatment can be better tailored.

Danielle Carnival, the White House cancer moonshot coordinator, says the administration is “really focused on how to bridge the gap” in cancer care for adolescents and young adults, “both in understanding the science and helping serve those patients better.”

The administration is closely following research into potential causes for the increase in cases and prioritizing “decreasing the impact of preventable cancers,” she says, including by working to further lower smoking rates and by “looking at nutrition and lifestyle.”

Bleyer, of the Knight Cancer Institute, points to lung cancer and melanoma as “examples of how we can do better” at preventing early-onset cancer. Both have beaten against the current in recent years, growing scarcer in the young even as other cancers have become more common. Researchers have linked lung cancer’s drop-off to the decline in smoking and melanoma’s to the embrace of sun protection.

For now, though, the overall rise in rates shows no sign of stopping. And it may be a canary in a coal mine.

“One of the reasons that we look at trends in younger adults is because it’s the best way to evaluate progress, because that’s where you first see changing patterns in cancer,” says Rebecca Siegel, a cancer epidemiologist and Senior Scientific Director of Surveillance Research at the American Cancer Society.

Several cancer researchers I spoke to agree: The age group now passing through adolescence and young adulthood, who were buffeted by a not yet fully understood cocktail of risk factors in the early years of their lives, will likely continue to suffer higher rates of cancer as they get older. 

It’s already happening, at least for colorectal cancer, Siegel says: Since 2010, advanced cancers of that type have become more common among Americans aged 50 to 64. 

“The younger people have elevated risk their whole life,” says Siegel. “As they age, they will carry that elevated risk with them.” 

Nathaniel Weixel contributed to this report.