The Enigma of “Early-Onset” Cancers: why are youthful Tumors on the rise?

For a long time, cancer has been considered a disease primarily linked to aging. Today, however, epidemiological data tell a more complex story.

By the end of 2025, a surprising picture emerges: while overall cancer mortality decreases thanks to targeted therapies, the incidence of tumors among adults under 50—known as early-onset cancers—is rising.

An analysis reported by the New York Times and supported by studies published in Annals of Internal Medicineindicates that six types of cancer are increasing significantly in younger age groups: breast, colorectal, endometrial, kidney, thyroid, and certain leukemias. Among these, colorectal carcinoma raises particular concern: it is the only one increasing more rapidly in young people than in those over 50.

The trend is also visible in Italy. AIOM 2025 data report over 15,000 new diagnoses each year among those under 40.

But what are the causes?

The main suspected factors remain well-known: obesity, sedentariness, and consumption of ultra-processed foods. These elements promote a state of low-grade chronic inflammation, which can create a biological terrain conducive to tumor development. However, research is broadening its perspective toward a more comprehensive concept: the exposome, that is, the totality of environmental and behavioral exposures that accompany an individual from conception onward.

Among the most studied hypotheses is the role of the gut microbiota.

Imbalanced diets and early antibiotic use can alter its composition, influencing the immune system and potentially facilitating pro-tumorigenic microenvironments.

Parallelly, the impact of widespread environmental chemicals, such as plastics and pesticides, is being investigated; these may interfere with hormonal balance. Some studies suggest a possible link with the anticipation of menarche and the rise in hormone-sensitive tumors, such as breast and endometrial cancers.

Social and reproductive changes may also play a role. The postponement of the age at first pregnancy reduces periods of natural hormonal protection, a factor that could contribute to the increase in cases among young women.

An additional paradox concerns screening.

In older populations, effective prevention programs—for example, the removal of precancerous polyps in the colon—have reduced disease incidence. Young people, however, often do not qualify for standard protocols and receive later diagnoses, sometimes when symptoms are underestimated precisely because of their age.

For this reason, medicine is rethinking prevention strategies.

The goal is no longer just to set an age threshold, but to develop personalized screening based on each individual’s genetic, metabolic, and environmental risk profile.

The challenge of the coming years will thus be twofold: to treat better, but above all to understand earlier. Because the “new epidemiology” of cancers is not addressed only in hospitals, but also by studying the biological and environmental vulnerabilities that build up over the entire lifespan.

Article written by prof. Antonio Giordano