All cancers are on the rise worldwide, in people under the age of 50

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The cause of almost 10 million deaths in 2020, almost one in six deaths according to the WHO, cancer is a leading cause of death worldwide. It’s a public health burden. Researchers recently sounded the alarm by revealing that in recent decades, more and more adults under the age of 50 have been diagnosed with cancer. Researchers are identifying the risk factors and trends behind a rising incidence of early-stage cancer worldwide, setting the stage for future research and prevention plans.

Cancer is a multifactorial disease that most commonly affects people over the age of 50. However, there is evidence that cancers of various organs (breast, colon, endometrium, esophagus, extrahepatic bile ducts, gallbladder, head and neck, kidneys, liver, bone marrow (multiple myeloma), pancreas, prostate, stomach and thyroid) occur increased in adults under the age of 50 in many parts of the world.

The increased use of screening programs has contributed to this phenomenon to some extent, although there also appear to have been genuine increases in the incidence of early forms of several cancers. Because of this growing cancer burden in young adults, called “ the early cancer epidemic » The National Cancer Institute of the United States has identified this phenomenon as a research priority.

Additionally, it was a study conducted by researchers at Brigham and Women’s Hospital, a founding member of Mass General Brigham, that uncovered this increasing incidence of early-stage cancer. This drastic increase started around 1990. To understand this “ early cancer epidemic Scientists performed extensive analyzes of data available in the literature and online, including information on early exposures that may have contributed to this trend. The results are published in the journal Nature Reviews Clinical Oncology.

A survey reveals a generational problem

To conduct their study, Shuji Ogino and lead author Tomotaka Ugai, colleagues in Brigham’s Department of Pathology, first analyzed global data describing the incidence of 14 different cancer types that showed increased incidence in adults under the age of 50 from 2000 to 2012.

Next, the team looked for available studies that looked at trends in potential risk factors, including early exposures in the general population. Finally, the team reviewed the literature describing the clinical and biological tumor characteristics of early-stage cancer compared to late-stage cancer diagnosed after 50 years.

Shuji Ogino explained in a press release: Using our data, we have observed the so-called birth cohort effect. This effect shows that each successive group of people born later (say, a decade later) have a higher risk of developing cancer later in life, likely due to risk factors they were exposed to when they were young . We have found that this risk increases with each generation. For example, people born in 1960 had a higher risk of cancer before the age of 50 than people born in 1950, and we expect this risk to continue to increase across generations. “.

In fact, major intergenerational changes in the exposome have occurred since the mid-20th century. It should be noted that the exposome is a concept that corresponds to all exposures to environmental factors to which a human organism is subjected from its conception to the end of its life, undergoing development in the womb and completing the action of the genome. In this study, the key intergenerational changes include changes in diet, lifestyle, obesity, environment, and microbiome, all of which could interact with genomic and/or genetic vulnerabilities.

Important risk factors identified

Therefore, the authors hypothesized that factors such as diet and western lifestyle might contribute to ” the early cancer epidemic “. As previously mentioned, the team recognized that this increased incidence of certain types of cancer is in part due to cancer screening programs. Although they could not measure exactly what proportion is due to screening alone, they found that the increased incidence of the majority of 14 types of cancer can be attributed to this early detection alone.

In fact, according to the authors, likely risk factors for early-stage cancer include alcohol consumption, smoking, obesity, consumption of highly processed foods and sugary drinks, type 2 diabetes, and physical inactivity. All of these factors have increased dramatically since the 1950s, which the researchers believe coincides with the changing microbiome.

Individual stresses throughout life and their relationship to the development of early-stage cancer. A person experiences various exposures throughout their life from conception, some of which could also be risk factors for cancer. © T. Ugai et al., 2022

Tomotaka Ugai underlines and then explains: Of the 14 types of cancer we studied, eight were linked to the digestive system. The food we eat feeds the microorganisms in our gut. Diet directly affects the composition of the microbiome, and it is possible that these changes can influence disease risk and outcomes “.

Surprisingly, the researchers found that while adult sleep duration has not changed drastically over the decades, children today sleep much less than decades ago, identifying sleep deprivation as a risk factor for developing early-stage cancer.

However, one of the limitations of this study is the lack of data from low- and middle-income countries to identify trends in cancer incidence over decades. In the future, Ogino and Ugai hope to continue this research by collecting more data and collaborating with international research institutes to better monitor global trends. They also explained the importance of conducting longitudinal cohort studies, with parental consent, to include young children that can be followed over several decades.

Tomotaka Ugai summarizes: Without such studies, it is difficult to determine what a person with cancer was doing decades ago or in their childhood. […] I think this will give us more accurate information about cancer risk for generations to come. “.

Finally, in-depth studies of risk factors and molecular properties of tumors in multiple types of early-stage cancer could also shed light on plausible common etiologies. In addition, better knowledge of the pathogenesis can inform strategies for primary prevention, early detection, and treatment.

Source: Nature Reviews Clinical Oncology

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