Appendix cancer cases have increased by up to four times among those born in the 1980s.

There is a trend that concerns and alarms oncologists: tumors in individuals under 50 have been growing for years, and the reason is unknown. In 2024, a study estimated this increase globally at nearly 80% over three decades. Another similar study from the same year, focused on colon cancer, noted increases in incidence in 27 out of 50 countries examined.

Today, the journal Annals of Internal Medicine publishes an epidemiological study showing that appendiceal cancer is becoming more common among individuals 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 those born in 1985 face nearly four times the risk. While the increase is observed across all types of appendiceal tumors, some subtypes are rising even more than others. For instance, the cancer of goblet cells has increased nearly five times in the 1980 cohort compared to the 1945 cohort.

Appendiceal cancer, a small pouch of tissue in the abdomen attached to the first segment of the large intestine, is very rare. According to U.S. data, there were one or two cases per million, and the causes of these tumors are not well understood. The authors of the study, led by Andreana Holowatyj from Vanderbilt University, believe that despite the low incidence, its increase among younger individuals suggests that as these individuals age, the number of cases will rise, and monitoring could help health systems be prepared.

María José Sánchez, scientific director of the Institute of Biosanitary Research of Granada and professor at the Andalusian School of Public Health, highlights the quality of the study and points out some of the hypotheses proposed by the authors regarding their findings. “They suggest it cannot be an accidental finding because the number of appendectomies, in which these tumors could be discovered, has decreased, but it may be related to something that Australian researchers have also observed: appendicitis is being treated less with surgical intervention and more with antibiotics, and this increased use of antibiotics could be related to this and other types of cancer,” Sánchez explains.

Furthermore, the rise in appendiceal cancer does not seem to be an isolated case. Other gastrointestinal tumors, such as those of the rectum, stomach, and colon, are also increasing, 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 do not have a model that can explain what is happening,” notes Josep Maria Borràs, scientific coordinator of the Cancer Strategy of the National Health System, referring to the increase in tumors among individuals under 50.

“It seems that the explanation could be the habits of young people, low physical activity, changes in diet, and high obesity rates, but we need more time to see what happens. We do know that it is unrelated to the classic hereditary colon and rectal cancers,” he continues. In Spain, studies like the one published in 2024 by The Lancet Oncology did not register the increase in colon cancer observed in half of the countries studied, “but that does not mean it will not 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 Annals of Internal Medicine confirm that increases have been detected in cases of the 34 most common types of cancer among individuals aged 25 to 84. However, the incidence is increasing more markedly among younger generations, which points to changes in lifestyle or environmental factors related to modern life.

Some researchers investigating the causes behind these epidemiological observations have found that, at a molecular level, young patients have tumors resembling those of older individuals. This has led to the hypothesis that changes in our environment may be causing accelerated aging. In an article published in Jama Oncology this year, three researchers from the National Cancer Institute of the U.S. pointed to several factors that could explain the accelerated biological aging of millennials and subsequent generations.

Although there is no consensus on the causes of the obesity increase in recent decades, there is agreement that it raises the risk of diseases like cancer. Low physical activity or a diet lacking variety and high in ultra-processed foods have also been identified as contributing factors. Among environmental factors, exposure to microplastics has been cited, as well as psychosocial conditions such as increased depressive symptoms, social isolation, or financial insecurity.

The accumulation of all these factors throughout life may be accelerating the biological clock, leading to the earlier onset of diseases related to aging. The authors emphasized that cancer is not the only disease that appears sooner. The same applies to strokes and heart failure.

María José Sánchez, who is also director of the Cancer Registry of Granada, agrees with another conclusion of the authors, calling for attention to these types of tumors. “We must consider that what happens in the U.S., after 15 years, happens in Spain and Europe,” she asserts. “Previously, we had very few cases of appendiceal cancer in our population. For one million people, some years there was one case, some years none, but since 2015, we have seen an increase, and in some years we have recorded as many as 10 cases, and that is something we need to monitor,” she concludes.