Recent studies have shown increasing rates of early-onset cancers, often defined as cancers occurring in people younger than age 50, especially colorectal, pancreatic, female breast, and uterine cancers, and younger birth cohorts seem to have a higher risk of some cancer types compared with older birth cohorts. A study by researchers at the National Cancer Institute (NCI) investigating cancer incidence in the United States between 2010 and 2019 has found that breast, colorectal, endometrial, pancreatic, and kidney cancers are becoming more common among individuals younger than age 50. Although the study did not find concomitant increases in mortality rates for most cancers, it showed that colorectal, uterine, and testicular cancer mortality rates also increased among younger adults. The findings may have implications for early-onset cancer prevention and screening efforts. The study by Shiels et al was published in Cancer Discovery.

Study Methodology

To identify cancer incidence and mortality rates in younger adults compared with older adults, the researchers analyzed incidence data from 2010 to 2019 in the U.S. Cancer Statistics database and cancer mortality data from 2019 to 2022 using national death certificate data from the National Center for Health Statistics. They conducted a detailed analysis of cancer incidence, including analyses of cancer subtypes, stage at diagnosis, and mortality trends, for 33 cancer types among younger age groups, including 15–29-, 30–39-, and 40–49-year-olds compared with older age groups, including 50–59-, 60–69-, and 70–79-year-olds.  

Key Results

The researchers found that among the 2,020,829 cases of early-onset cancers diagnosed between 2010 and 2019, 63.2% were diagnosed in females. The most common early-onset cancer types included breast cancer, thyroid cancer, and melanoma among female patients and colorectal cancer, testicular cancer, and melanoma among male patients.

They also found that overall trends in early-onset cancer incidence rates seem to be driven by heterogeneous trends across cancer types. For example, of the 33 cancer types included in their analysis, 14 cancer types had significantly increasing incidence rates in at least one early-onset age group, and 19 cancer types had significantly decreasing incidence rates in the most recent time period in at least one early-onset age group.

The incidence of five of these cancer types—melanoma, plasma cell neoplasms, cervical cancer, stomach cancer, and cancer of the bones and joints—increased in at least one early-onset age group without corresponding increases in any late-onset age group. The remaining nine cancer types—female breast cancer, colorectal cancer, kidney cancer, testicular cancer, uterine cancer, pancreatic cancer, precursor B-cell non-Hodgkin lymphoma, diffuse large B-cell lymphoma, and mycosis fungoides/Sézary syndrome—had significantly increasing incidence in at least one early-onset and one late-onset age group.

The researchers’ analyses showed that the largest absolute increases in 2019 compared with expected diagnoses based on 2010 rates were female breast cancer (n = 4,834 additional cancers); colorectal cancer (n = 2,099), kidney cancer (n = 1,793), and uterine cancers (n = 1,209). Together, these cancers accounted for more than 80% of the additional cancer diagnoses in 2019 compared with 2010.

Of the 14 cancer types with increasing incidence rates, 4 cancer types—testicular cancer, uterine cancer, colorectal cancer, and cancer of the bones and joints—also had increasing mortality rates in at least one age group. The remaining 10 cancer types exhibited increasing incidence without increasing mortality for any age group.

“The drivers of increasing incidence rates are cancer-specific and could include a combination of established and perhaps new etiologic factors, and increased detection,” concluded the study authors.

Clinical Significance

Although incidence rates of some cancers have increased in early-onset age groups, for many of these cancers, rates have also increased in older age groups, suggesting, according to the researchers, that the impact of changes in risk factor prevalence and/or improvements in detection may affect risk across various age ranges. “The increasing incidence of many cancer types in younger and older age groups suggests that there may be risk factors that impact cancer development across ages or advances in screening or imaging technologies that allow cancers to be detected more frequently than before,” said Meredith Shiels, PhD, MHS, the first author of this study and Senior Investigator in the Infections and Immunoepidemiology Branch of the NCI, in a statement.

Disclosure: Funding for this study was provided by the National Cancer Institute. Dr. Shiels reported no conflicts of interest. For disclosures of the other study authors, visit https://aacrjournals.org/cancerdiscovery.