Cases of appendix cancer increased up to fourfold among those born in the 1980s.

There's a trend that intrigues and alarms oncologists: tumors in people under 50 have been growing for years, and no one knows why. In 2024, a study estimated this global increase at nearly 80% over three decades. Another similar study from the same year, focused on colon cancer, found increases in incidence in 27 of the 50 countries examined.

Today, the Annals of Internal Medicine published an epidemiological study showing that appendix cancer is becoming more common among people born in the U.S. in recent decades. Those born in 1980 are three times more likely to develop it than those born in 1945, and for those born in 1985, the risk is nearly four times higher. And while the increase is seen across all types of appendix tumors, some subtypes are growing even more than others. For example, goblet cell cancer has increased nearly fivefold in the 1980 cohort compared to the 1945 cohort.

Cancer of the appendix, a small sac of tissue in the abdomen attached to the first section of the large intestine, is very rare. According to US data, there were one or two cases per million, and the causes of these tumors are not fully understood. The study's authors, led by Andreana Holowatyj of Vanderbilt University, believe that despite the low incidence, the increase in incidence among younger people suggests that, as these individuals age, the number of cases will increase, and surveillance can help prepare healthcare systems.

María José Sánchez, scientific director of the Granada Biosanitary Research Institute and professor at the Andalusian School of Public Health, highlights the quality of the study and points to some of the hypotheses put forward by the authors regarding their results. "They suggest that this cannot be an accidental finding, because the number of appendix surgeries, in which these tumors could be discovered, has decreased, but it could be related to something that Australian researchers have also observed: appendicitis is treated less with surgery and more with antibiotics, and this increased consumption of antibiotics could be linked to this and other types of cancer," explains Sánchez.

Furthermore, the increase in appendix cancer does not appear to be an isolated case. Other gastrointestinal tumors, such as those of the rectum, stomach, and colon, are also on the rise, suggesting that there may be a common cause, related to diet or environment, that is affecting younger generations. "There is no clear risk factor, and we don't have a model that can explain what is happening," says Josep Maria Borràs, scientific coordinator of the National Health System's Cancer Strategy , referring to the increase in tumors in people under 50.

“It seems that the explanation could be young people's habits, low physical activity, changes in diet, and high obesity rates, but we need more time to see what happens. We do know that it has nothing to do with traditional hereditary cancers of the colon and rectum,” he continues. In Spain, studies such as the one published in 2024 by The Lancet Oncology did not record the increase in colon cancer observed in half of the countries studied, “but that doesn't mean it won't be seen in the future, because there have been changes in lifestyle,” warns Borràs.

Other studies referenced by the authors of the article published in the Annals of Internal Medicine confirm that increases in cases of the 34 most common types of cancer have been detected among people aged 25 to 84. However, the incidence is increasing most significantly among younger generations, which may indicate changes in lifestyle or environmental factors related to modern life.

Some researchers searching for the causes that explain these epidemiological observations have observed that, at the molecular level, young patients have tumors that resemble those of older people. This has led to the suggestion that changes are occurring in our environment that are causing accelerated aging. In an article published in JAMA Oncology this year, three researchers from the US National Cancer Institute pointed to several factors that could explain the accelerated biological aging of millennials and later generations.

Although there is no consensus on the causes of the rise in obesity in recent decades, there is consensus regarding the fact that it increases the risk of diseases such as cancer. Low physical activity or a diet with limited variety and too many ultra-processed foods were also among the factors cited. Among the environmental factors, exposure to microplastics was noted, and psychosocial factors were also considered, such as increased depressive symptoms, social isolation, and financial insecurity.

The accumulation of all these factors throughout life could accelerate the biological clock, with the consequent earlier onset of aging-related diseases. The authors emphasized that cancer isn't the only disease that appears earlier. The same is true for strokes and heart failure.

María José Sánchez, who is also director of the Granada Cancer Registry, agrees with another of the authors' conclusions, which call for attention to be paid to this type of tumor. "We have to remember that what happens in the US, at age 15, also happens in Spain and Europe," she says. "Previously, we had very few cases of appendix cancer in our population. For every million people, some years there was one, some years there were none, but since 2015 we've seen an increase, and some years we've recorded up to 10 cases, and that's something we have to monitor," she concludes.