The Emerging Epidemic of Early-Onset Cancer: Global Patterns, Biological Complexity, and Urgent Calls for Action.

Cancer is often considered a disease of older adults, yet in recent decades an increasing number of people under the age of 50 have been diagnosed with cancer worldwide. According to global data, the most common early-onset cancers include breast, tracheal/bronchus/lung, stomach, and colorectal cancers, followed by thyroid, pancreas, and liver malignancies. These cancers often behave more aggressively than those diagnosed later in life and contribute substantially to premature mortality and disability. Researchers believe that this trend is driven less by hereditary syndromes and more by cumulative environmental and lifestyle exposures beginning early in life. Diets high in ultra-processed foods, reduced physical activity, antibiotic overuse, pollution, psychosocial stress, and disruptions of the gut microbiome have all been implicated as potential contributors. Unlike inherited cancer syndromes, most early-onset cancers are sporadic, arising from complex interactions between modifiable exposures and host biology. Younger patients face unique challenges: they are underrepresented in clinical trials, often lack access to age-appropriate multidisciplinary care, and experience disruptions to education, employment, and family planning. Addressing this growing public health concern requires earlier screening for high-risk groups, investment in adolescent and young adult (AYA)-specific biorepositories and research, and policies that prioritize prevention, equity, and tailored care for younger populations.