Cancer in individuals younger than 50 years accounts for a growing proportion of cases globally, with distinct patterns in prevalence and characteristics compared to older adults.
New cancer diagnoses among people under 50 totaled approximately 3.26 million cases in 2019, representing a 79% increase from the 1.82 million cases in 1990 .
In the US, the annual incidence of early-onset cancer (under 50) has increased modestly over the past decade, with approximately 56,000 new cases diagnosed in 2019.
Globally, about 9% of all cancers occur in people younger than 40 years, and adolescent and young adult (AYA) cancers (15–39 years) represent 7–8% of all cases.
In the United States specifically, a nationwide analysis found a higher incidence of 14 types of cancer among people under 50 years old compared to rates in 2010 .
Breast cancer accounted for the largest number of early-onset cases and deaths, while the fastest increases were seen in cancers of the tracea and prostate .
Gastrointestinal cancers showed the fastest-growing incidence rates among all early-onset cancer groups, particularly cancers of the appendix, intrahepatic bile duct, and pancreas .
Colorectal cancer has been particularly notable, with rates rising sharply in younger adults while declining in those over 50.
Research suggests several potential causes for this increase:
Diets high in red meat and salt and low in fruit and milk, along with alcohol consumption and tobacco use, are the main risk factors underlying the most common cancers among the under 50s, with physical inactivity, excess weight, and high blood sugar as contributory factors.
A birth cohort effect shows that each successive group of people born later have a higher risk of developing cancer, likely due to risk factors they were exposed to at a young age .
Changes in the early life exposure, including diet, lifestyle, weight, environmental exposures, and the microbiome—may be playing a significant role.
Despite the increase in diagnoses, cancer deaths in young people have not increased overall.
Screening guidelines have been updated in response, with recommended ages for colorectal cancer screenings lowered from 50 to 45 years, and breast cancer screenings lowered from 50 to 40 years .
The most common cancers in this age group are breast, thyroid, colorectal, cervical, and testicular cancers.
Breast cancer is the leading diagnosis among women, while colorectal and testicular cancers are most common in men.
Thyroid cancer incidence has risen sharply, especially in women, but much of this increase is attributed to overdiagnosis.
Gastrointestinal cancers (colorectal, stomach, pancreas) are notable for their rapidly increasing incidence rates, particularly among younger adults.
Characteristics of early-onset cancers include:
More aggressive biology and poorer prognosis for some types-colorectal, breast, compared to later-onset cases.
Higher rates of sporadic disease, though familial syndromes (e.g., BRCA, Lynch, FAP, Li-Fraumeni) contribute to a minority of cases and confer substantial risk.
Unique challenges for younger patients, including: fertility, education, employment, and psychosocial well-being.
Rates have increased among women driven by breast and uterine cancers and in certain racial/ethnic groups (American Indian/Alaska Native, Asian/Pacific Islander, Hispanic).
Internationally, increases are most pronounced for thyroid, breast, colorectal, kidney, endometrial, and leukemia in younger adults.
In summary, early-onset cancer is increasingly recognized, with breast, thyroid, colorectal, and testicular cancers most prevalent. The rise in incidence is multifactorial, involving both true increases and greater detection, and younger patients face distinct clinical and social challenges.