Experts from half the planet are warning of a disturbing phenomenon. Colorectal cancer cases are declining among the elderly but are skyrocketing among those under 50 worldwide. According to two of the world’s leading specialists, Kimmie Ng and Marios Giannakis of the Dana-Farber Cancer Institute, the incidence has been increasing at an “alarming” rate of about 3% per year in many countries, with the under-30s increasing even faster. in Boston (United States). The causes of this puzzling process are intuitive but unknown.
Oncologist Kimmie Ng says she sees it every day at her hospital. “We have spent many years treating increasing numbers of very young patients admitted with already metastatic colorectal cancer, many of them with no genetic predisposition or obvious risk factors,” he points out. They are women and men in their 20s, 30s or 40s who have had non-specific symptoms such as constipation or diarrhea for months without anyone their age suspecting cancer. The doctor thinks the situation is “extremely worrying” and urges the scientific community to come together to understand what is happening. Their call to action will be published this Thursday in Science magazine.
Colorectal cancer, which kills nearly a million people every year, is the second most common cancer in the world after lung cancer. The team led by Rebecca Siegel, chief scientist at the American Cancer Society, warned as early as 2019 that this cancer was increasing in the under-50s in at least 19 countries. In a dozen of them, these tumors decreased in people over the age of 50 but increased rapidly in younger adults, as in New Zealand (4% per year), the United Kingdom (3.3%), Canada (2.8%) , Australia (2.8%), United States (2.2%), Sweden (1.6%) and Germany (1.3%).
We have been seeing more and more very young patients for many years
Kimmie Ng, oncologist
The two researchers from the Dana Farber Cancer Institute admit that the exact reasons for this phenomenon are “unknown”, but they list the main hypotheses. “We suspect that environmental factors such as diet and lifestyle contribute,” explains Kimmie Ng. “We have identified obesity, lack of exercise, increased consumption of sugary drinks and vitamin D deficiency as risk factors,” he emphasizes.
In Spain there is no national cancer database because no government devotes resources to it, but there are a few dozen local registers covering 27% of the country’s population. The president of this Spanish network of cancer registries, the epidemiologist Jaume Galceran, points out that none of the three major western Mediterranean European countries – Spain, Italy and France – have seen an increase in incidence rates, at least for the moment.
Galceran explains that colon cancer figures in Spain remain “stable”, with one annual case per 15,000 people under the age of 50, according to their data for the period 2002-2016. However, as the epidemiologist acknowledges, local records are scarce in the central and southern parts of the country, where some of the regions with the greatest problems with childhood and adolescent obesity are concentrated. Galceran, in charge of the Tarragona cancer registry, urges the Spanish authorities to rely on a single national registry. “It’s a question of will and resources,” he says.
The epidemiologist does not rule out that this uptick in colon cancer among young adults will eventually reach Spain, a country where obesity and a sedentary lifestyle are on the rise, as was the case in Britain and the United States decades ago. the oncologist Ana Fernandez Montes, from Ourense University Hospital Complex, believes this is already happening. “In Spain we don’t have a national register that tells us that the incidence is increasing, but we have the impression that it is happening. We have more and more young people. I just got a 36-year-old boy,” he explains.
The same will happen here because of the habits of life that we lead
Ana Fernández Montes, oncologist
Fernández Montes, board member of the Spanish Society of Medical Oncology, fears the rate of growth seen in countries like the United States. “It’s barbarism. And the same thing will happen here because of the lifestyles we lead. We’re already seeing an alarming increase in young people,” he says. The oncologist recalls a recent US study suggesting that the Drinking two or more sugary drinks a day doubles the risk of developing colon cancer before the age of 50. “The message is that you have to have healthy lifestyle habits: exercise, don’t drink sugary drinks, avoid highly processed products,” proclaims the Physician.
The biotechnologist Cayetano Pleguezuelos names other protagonists: the bacteria of the digestive system. “In my view, the most noticeable are changes in the intestinal microbiota,” says the Spaniard from the Hubrecht Institute in the Netherlands. For the first time, his team showed a direct connection between these bacteria and the cancer-causing DNA damage in human cells.
Pleguezuelos explains that junk food itself changes the composition of bacterial communities in the gut, but acknowledges that the science in this area is still in its infancy. “We still don’t know exactly which factors contribute to these changes in the microbiota or which bacteria [están vinculadas al cáncer]”, he agrees. The biotechnologist is collaborating with Kimmie Ng herself in an international consortium called Optimisticc to study the effects of gut microbes on colon cancer. In October, a Yale University group pointed to the bacterium Morganella morganii, common in the human gut, as a putative cause of these tumors.
Oncologists Kimmie Ng and Marios Giannakis predict that by 2030, early-onset colorectal cancer will be the leading cause of cancer-related death in people aged 20 to 50. The authors suggest strengthening screening programs in young adults, as has been done in the United States, where testing for occult blood in the stool is recommended from age 45. In Spain, these tests are carried out from the age of 50.
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