The increase in cancer cases among young adults keeps oncologists in suspense. So much so that the congress of the European Society of Medical Oncology (ESMO), held a few days ago in Barcelona, dedicated a talk to discussing this topic and the room was packed. Hundreds of oncologists from around the world attended the presentation by Shuji Ogino, professor of Epidemiology at Harvard Medical School, about this “emerging global epidemic” that is causing specialists to be overwhelmed. According to a study published in the journal BMJ Oncology, Tumors in people under 50 years of age have grown by almost 80% in three decades, but scientists have not yet been able to fully unravel this phenomenon. The experts consulted assure that current lifestyle habits are having an influence, although this variable, by itself, may not explain everything. According to Ogino, the increase in early-onset cancer is only “the tip of the iceberg” of a global rise in chronic diseases over several generations.
“We are seeing an increase in cases in young patients and we are concerned because it is not always related to a specific cause,” confirms Ángela Lamarca, oncologist at the Jiménez Díaz Foundation and spokesperson for the ESMO congress. Colorectal cancer is where this emerging dynamic is most studied, but it also occurs in other tumors, such as pancreas, esophagus, kidney, liver, bile ducts, gallbladder, stomach, head and neck tumors, or breast cancer, among others. others. “Several studies have been done to analyze whether there is a molecular cause that explains why more cases occur in young patients and, many times, we have been surprised that, at a molecular level, young patients have tumors very similar to those that occur in older patients. We still need to investigate and understand more if there is something at a molecular level that we have not been able to identify or if it is something related to risk factors,” says Lamarca.
The origin of early-onset cancer is unclear. It is probably multifactorial. The researchers consider that, although greater and better detection of certain tumors may have had an influence, this would not explain the overall increase in cases, since some do not have early detection tests and, furthermore, most screening is usually carried out after of 50 years, not before. Family history and hereditary syndromes, on the other hand, may justify a portion of new diagnoses, but they are not the most frequent profiles either. The majority of cases are sporadic (without family or hereditary link) and remain without a clear explanation.
Lamarca gives the example of pancreatic cancer. They are seeing cases of 40 years old, when it was usual to see it in people over 65: “We thought that young patients developed pancreatic cancer for some reason that made them have a higher risk, but we have not always found it. Yes, it is true that there are hereditary syndromes, such as BRCA. [personas que presentan mutaciones en estos genes]which is also associated with breast and ovarian cancer, which can justify pancreatic cancer in a young person, but these are not all the young patients we find. So, why do these young patients develop pancreatic cancer that, when analyzed at a genetic level, is the same as what we see in a 65-year-old? We don’t know,” laments the oncologist.
What the scientific community is clear about is that (bad) lifestyle habits play a fundamental role. Western diets (rich in carbohydrates and processed food) that promote obesity do not help, nor does a sedentary lifestyle, nor toxic habits such as tobacco and alcohol, explains David Páez, an oncologist specialized in digestive tumors at the Sant Pau Hospital in Barcelona: “ The risk factors are the same as for cancer in older adults, but it is not known if there is something else influencing that explains the early appearance of cancer only due to these factors and in some populations,” he outlines. The study itself published in BMJ Oncology concludes that “dietary risk factors, alcohol consumption and tobacco consumption were the main risk factors for the main early-onset cancers” recorded in 2019. But it adds that “it is necessary to carry out prospective cohort studies throughout of life to explore the etiologies [las causas] of early-onset cancers.
Risk exposures from childhood
What matters is now, current behavior, but also yesterday and the entire environment in which a person has developed throughout their life. And even before being born. Páez points to the key role of the exposome, which are all those non-genetic factors to which an individual is exposed throughout their life and determine their health: “The interaction of these external factors with the genome can condition the appearance of diseases. “It is thought that these factors may be altering people’s immunity or the composition of the microbiome from the prenatal period.”
A group of Harvard researchers (including Ogino) reflect along the same lines in a study and highlight that the earliest phase of carcinogenesis could begin very soon: “Exposures in utero can lead to cellular reprogramming, including epigenetic alterations, which could have lasting effects on susceptibility to chronic diseases.” In fact, they suspect that reproductive factors (age at onset of menarche, having received or not breastfed, fertility rate, use of oral contraceptives…), as well as smoking, diet, alcohol consumption, lifestyle and previous illnesses of the mother during pregnancy “could be relevant intrauterine exposures.”
Exposure to long-term risk factors begins in the first years of life. “What we see now is the result of decades of exposure.”
Shuji Ogino, Professor of Epidemiology at Harvard Medical School
In this sense, during the presentation at ESMO, Ogino once again emphasized that, probably, “nature and nurture” influence early-onset cancer. “Exposure to long-term risk factors begins in the first years of life. “What we see now is the result of decades of exposure,” he recalled. What scientists are also not clear about is how much each risk factor weighs at a given moment in life and how they interact with each other.
Precisely because of the long latency time that cancer has and the change in exposure to various environmental and life factors, experts emphasize the importance of the birth cohort effect in colon cancer. This means that each generation experienced a higher risk of early-onset cancer than the previous one. In a magazine podcast ScienceKimmie Ng, a researcher at the Dana-Farber Cancer Institute in Boston (USA), who has described the rise of colorectal cancer in young adults, explained that “it is something that is affecting generation after generation, where people born in 1990 have a significantly higher rate of developing colorectal cancer compared to people born in 1950.” And he added: “We believe it is due to environmental exposure. To what exactly? We don’t know. Again, we’ve looked at obesity, we’ve also looked at sedentary behavior, higher consumption of sugar, sweets and drinks, lower levels of vitamin D, and they all seem to be associated with increased risk, but I don’t think that’s it. which explains what is happening.”
Later diagnoses
Scientists are also investigating the specific characteristics of these early-onset tumors, but it is a field full of unknowns. To begin with, these are unpredictable tumors, since there are no early detection tests to anticipate the diagnosis or screenings that appeal to these ages (they are usually from 50 years of age). At the consultation, oncologists highlight that they are discovered in advanced stages: “They are usually detected in symptomatic phases. In the case of colon cancer, for example, when there is bleeding with stool, abdominal pain or changes in intestinal habits. What we see is a diagnostic delay with respect to older adults and in young people it takes about six months longer to diagnose,” explains Páez.
Some research also warns that these are more aggressive tumors, but it is not resolved whether this is due to the biology of this cancer itself, which is more virulent, or because it is diagnosed in advanced stages. “In the colon, it is not clear if there are molecular differences between tumors in older and younger adults. The worse prognosis is more attributed to the diagnostic delay,” points out the Sant Pau oncologist. An article by researchers from the University Hospital of Navarra, who have designed a study to analyze early-onset cancer in northern Spain, broadens the focus and assures, however, that early-onset gastrointestinal tumors “present in clinical stages advanced and with aggressive phenotypes.”
In any case, the approach to these patients poses new challenges for specialists. The treatment is the same as if they were older adults, but the consequences of this diagnosis differ in the young population, warns Páez: “It is a challenge from the point of view of the consequences that may remain from the type of treatment or surgeries and its impact on quality of life. And then the long-term risk of developing another cancer is also higher.” The oncologist also points out more psychosocial problems, stigma, impact on mental health and impact on work life or even reproductive or sexuality-related aspects.
For now, the tools to tackle this phenomenon are limited. “Dissemination and awareness” about the situation, avoiding risk factors and continuing to investigate, says Páez, to see if it makes sense to lower the age of screening (in the United States it has been done, but it is still under discussion among scientists) and to find early detection tools.
Pedro Pérez Segura, member of the Permanent Commission of the ECO Foundation and head of Medical Oncology at the San Carlos Clinical Hospital (Madrid), also advocates “educating” citizens to improve lifestyle: “We are witnessing a new boom of tobacco and alcohol in younger population. And we live in a time in which a sedentary lifestyle is important. We must reinforce health education to avoid all this and also remember the importance of sun protection because the incidence of skin lesions is also growing.”
Lamarca also calls on the population to consult when they have symptoms, not to underestimate them: “If you have symptoms, go to the doctor. Many times, a young patient may have symptoms, such as weight loss, abdominal pain or other non-specific things, and they don’t give it importance because they say: ‘what is cancer going to be like if I’m 40 years old?’ Well, the reality is that there are more and more cases of cancer diagnosed in the young population and many times they are diagnosed later, precisely because they do not go to the doctor, because they minimize the symptoms.”