Gen X and millennials at higher cancer risk than older generations

Generation X and millennials are at an increased risk of developing certain cancers compared with older generations, a shift that is probably due to generational changes in diet, lifestyle and environmental exposures, a large new study suggests.

In a new study published Wednesday in the Lancet Public Health journal, researchers from the American Cancer Society reported that cancer rates for 17 of the 34 most common cancers are increasing in progressively younger generations. The findings included:

• Cancers with the most significant increased risk are kidney, pancreatic and small intestine, which are two to three times as high for millennial men and women as baby boomers.

• Millennial women also are at higher risk of liver and bile duct cancers compared with baby boomers.

• Although the risk of getting cancer is rising, for most cancers, the risk of dying of the disease stabilized or declined among younger people. But mortality rates increased for gallbladder, colorectal, testicular and uterine cancers, as well as for liver cancer among younger women.

“It is a concern,” said Ahmedin Jemal, senior vice president of the American Cancer Society’s surveillance and health equity science department, who was the senior author of the study.

If the current trend continues, the increased cancer and mortality rates among younger people may “halt or even reverse the progress that we have made in reducing cancer mortality over the past several decades,” he added.

While there is no clear explanation for the increased cancer rates among younger people, the researchers suggest that there may be several contributing factors, including rising obesity rates; altered microbiomes from unhealthy diets high in saturated fats, red meat and ultra-processed foods or antibiotic use; poor sleep; sedentary lifestyles; and environmental factors, including exposure to pollutants and carcinogenic chemicals.

Two decades of cancer data

Researchers analyzed data from more than 23.5 million patients who had been diagnosed with 34 types of cancer from 2000 to 2019. They also studied mortality data that included 7 million deaths from 25 types of cancer among people ages 25 to 84 in the United States.

Expanding on their previous research, which had identified eight types of cancer in which incidence rates increased with each successive generation, the researchers have found an additional nine, including some that had previously declined among older birth cohorts before rising in younger populations.

The study did not examine factors including household income, insurance status, race or ethnicity.

Younger people, or those under 50, represent a minority of the overall population of those who develop cancer, “but the concern is that cancer is occurring at younger and younger ages, so this increased incidence raises very real concerns as that population continues to age,” said Ernest Hawk, vice president and head of the division of cancer prevention and population sciences at the University of Texas MD Anderson Cancer Center.

At the same time, the researchers also noted that there has been a drop in cervical cancer rates among younger women, which they attribute to vaccination against the human papillomavirus (HPV). Smoking-related cancers such as lung, larynx and esophageal squamous cell carcinoma also declined, though progress has slowed among the youngest age groups, the researchers said.

Difficulties with detection

Routine screening tests are recommended for only four cancers - colon, cervical, breast and, for some people, lung - and a number of younger people who are at average risk do not meet the age requirements or, for various reasons, are not getting screened. Some experts have pointed to potential harms from widespread screening, including false positives that may take a psychological toll and lead to unnecessary follow-up tests and procedures.

“The problem becomes that patients are getting younger and younger, we don’t always have good screening to begin with, and then we can’t really screen such large populations,” said Andrea Cercek, a gastrointestinal oncologist and co-director of the Center for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Center.

In the new study, breast, gallbladder and other biliary cancers, and uterine cancer rates increased across almost all age groups, rising faster among younger generations. While breast cancer rates among women younger than 40 remain low, in a separate study, breast cancer still accounted for the highest number of early-onset cancer cases.

Lowering screening ages

Recent and growing evidence showing that more women in their 40s are getting breast cancer prompted the U.S. Preventive Services Task Force last year to change its previous guidance, lowering the age for routine screening mammograms from age 50 to 40.

Routine mammograms are not as effective for women with dense breasts, however, which is more common among those who are younger, said Elizabeth Comen, a breast cancer oncologist and associate professor at New York University Langone Health’s Perlmutter Cancer Center.

“Understanding how we can better screen and detect cancers in younger patients is a massive unmet need,” said Comen, who added that many of her younger patients find their own breast cancer.

In recent years, the recommended age for colorectal cancer screening was also lowered, from age 50 to 45, as research has shown a trend toward diagnoses at younger ages. The new study found that increases in stomach and colorectal cancer rates were confined to younger age groups, meaning that while colorectal cancer rates are declining overall, there is a rise in incidence in younger populations.

But many people who are eligible are not getting colorectal cancer screenings. A 2021 study reported that fewer than 4 million of the eligible 19 million adults ages 45 to 49 years were up-to-date on screenings, which can include a newly approved blood test, a stool test or a visual test such as a colonoscopy or CT colonography.

Even when symptoms arise, “I think many younger folks ignore them, thinking they cannot get cancer because they’re young,” said Rashmi Verma, an oncologist who specializes in gastrointestinal cancers at the Comprehensive Cancer Center at the University of California at Davis, adding that she has treated patients as young as 20.

Others may be uninsured or not aware that screening tests are recommended for them, experts said.

Missed diagnoses

When some younger patients seek care for gastrointestinal symptoms, they are misdiagnosed with other conditions such as hemorrhoids or irritable bowel syndrome, so it is important to consult a gastroenterologist, Verma said.

But for most cancers, including pancreatic cancer, there are no screening tests - at any age - which can lead to late diagnoses and more limited treatment options, experts said.

While there have been advances in diagnostics and treatment, oftentimes, malignant pancreatic tumors (and some others) are discovered incidentally during imaging for other issues, said Charles J. Yeo, a professor and chair of the department of surgery at Sidney Kimmel Medical College at Thomas Jefferson University.

The increasing cancer rates among younger generations highlights the need for further study to both pinpoint a cause for planning prevention as well as to develop better - and, in many cases, any - screening tests to help detect cancers in younger people earlier in the course of disease when treatment is often more effective, experts said.

The rising rates also raise questions about what happens to younger patients in survivorship.

“There are going to be young cancer survivors who are deeply impacted biologically, physically and psychologically from these diagnoses,” Comen said. “And that’s going to have a ripple effect in our society that our medical community needs to be equipped to address.”