There has been a higher and more prominent incidence of stomach cancer in northern districts for decades, but experts say it is difficult to point the finger at a single cause.
One in two stomach cancers are diagnosed in the north of the country. And although there is no exact explanation for the phenomenon, there are three factors that have proven to be decisive for 48% of cases to be diagnosed in this region of the country.
Leopoldo Matos, a gastroenterologist for more than three decades, says that “for a long time, it was thought that it had to do with the type of food”, something that, he adds, is still on the table because of “smoked and salty ”. A possible genetic cause was also studied, “but only 10% of stomach tumors have some familial aggregation, with very few families with a genetic code in which stomach cancer is dominant over other cancers”. “There is no obvious reason”, he says, saying that the greater number of stomach cancers in the North may have to do “with the environment and family”, lamenting that “there have not been enough studies” to outline one (or more than one) a) concrete cause.
Excluding breast cancer and cancers exclusive to each sex, stomach cancer is the fourth most common in Portugal. Of the 2,615 new cases diagnosed, 1,280 were in the North, followed by 394 cases in the Lisbon Metropolitan Area, 296 in the central region, 121 in Alentejo, 70 in the Algarve, 18 in Madeira and just six in the Azores. But looking by districts, Viana do Castelo, Braga and Porto stand out with 39% of the total number of new cases of stomach cancer, according to the most recent data from the National Oncological Registry (RON) 2020, released last year and referring to 2020. .
“In the general picture of stomach cancer, there are four fundamental aspects for the onset of the disease: infection by Helicobacter pylorisalt, alcohol and smoking”, points out doctor Pedro Narra Figueiredo, president of the Portuguese Society of Gastroenterology.
Although these are the most common denominators of stomach cancer, José Carlos Machado, professor at the Faculty of Medicine of the University of Porto and researcher at i3S, highlights that, “historically, what distinguishes the North and the South is the prevalence of Helicobacter pyloribut no one really knows why this is prevalent.”
The ‘poor’ bacteria
Diogo Libânio, hospital assistant in Gastroenterology at IPO Porto and assistant professor at the Faculty of Medicine of the University of Porto, says that “70% to 90% of gastric cancers are related to Helicobacter pylori, and Portugal is a country with a high prevalence of this bacteria”. “In studies at the beginning of the millennium we were the second country in the world”, he adds.
A Helicobacter pylori, a bacterium located in the gastric mucosa, was identified in 1982 and described as the “bacteria of the poor”, having for several years shown a Portugal with two rhythms in terms of wealth and poverty and, consequently, the best and worst living conditions , housing and sanitation. “A Helicobacter pylori it is associated with lower sanitary conditions, more unfavorable socioeconomic strata and the North, as a whole, is a poorer region. And having a higher incidence there causes the infection to perpetuate”, explains the also member of the Portuguese Society of Digestive Endoscopy (SPED).
“If we go back 100 years, infection by Helicobacter pylori it was hyper prevalent throughout the world, which is why stomach cancer was the most common cancer in the world. In many countries, the infection subsided spontaneously, it was an unplanned triumph. This may be due to the introduction of better hygiene habits and sanitation and sewage. But in southern European countries this took a long time to happen. Portugal is still behind, but we are on the path to reducing this infection. And the population density is higher in the North and when things are infectious it is easier to happen there, like tuberculosis”, explains José Carlos Machado.
Infection with this bacteria – included in the list of carcinogens by the United States Department of Health and Human Services in 2021 – is acquired during childhood and “is closely related to poor hygienic and sanitary conditions”, as explained on the Metis website, from Faculty of Medicine of the University of Porto, which reveals that, in 2013, the prevalence of infection was 80% in the entire Portuguese population. The prevalence of infection by Helicobacter pylori during the periods from 2010 to 2022 in Portugal was classified as “high” in the study published this year in Gastroenterology. But Diogo Libânio says that Portugal is on the right path and that the prevalence of this bacteria is decreasing, being fixed at “50%”.
CNN Portugal tried to obtain data from INSA on the incidence of Helicobacter pylori in Portugal, but did not receive any response in a timely manner.
Northern-style food
Red meat, sausages, smoked meats and wine are common on a rich northern table, but they are also commonly associated with eating habits that can increase the risk of stomach cancer. Pedro Narra Figueiredo is quick to associate sausages with salt and warn of the fact that “sausages are not part of the Mediterranean diet”. And he also remembers that red meat and processed meat were, in 2015, classified by the World Health Organization as potentially carcinogenic and carcinogenic, respectively.
“As for the greater consumption of meat and sausages, typical of northern cuisine”, despite arguing that food has a “clearly smaller effect” than Helicobacter pylori, researcher José Carlos Machado says that “excessive consumption of salt and smoked foods” can, in fact, be triggers for the disease, and in this last type of food, the issue is nitrosamine, found in cured meats, beer and other alcoholic beverages. This chemical compound can be genotoxic (damages DNA) and carcinogenic (can cause cancer). Still, José Carlos Machado highlights that the impact of diet on stomach cancer “is difficult to measure”.
Salt is another gastronomic element included in this equation. Although its consumption is widespread throughout the country, in the North it is still common to brine and use this ingredient to preserve food.
In 2022, one of several studies by the Stomach cancer Pooling (StoP) Project – a consortium that includes Portuguese researchers – focused on the impact of salt and concluded that “the preference for a salty taste, always using table salt, and a greater Intake of foods high in salt and preserved in salt increased the risk of gastric cancer.”
The trend is for there to be more cases
According to the International Agency for Research on Cancer (IARC), by 2045 Portugal will have 24.6% more new cases of stomach cancer, with more than 4,500 diagnoses annually. A sedentary lifestyle, poor diet and smoking are pointed out as triggers for this scenario (and for other types of cancer), but doctor Diogo Libânio also highlights obesity, saying that “an increase” in the number of gastric cancers related to excess weight and reflux (also a possible consequence of obesity). For this reason, he says that weight should be included in the primary cancer prevention strategy, which also includes “reducing salt consumption, avoiding tobacco and consuming more vegetables and fruits”.
But it is early screening that may be the key to lowering the mortality rate, which, according to RON 2020, stands at 81% – although there is a decline, as experts interviewed by CNN Portugal point out. The current Executive’s program wants to extend screenings to gastric cancer (in addition to lung and prostate), a proposal that was already included in the State Budget for 2024, still supervised by António Costa, and which is based on a recommendation from the European Commission.
“With the high incidence of stomach cancer that we have in our country, which is higher than in the rest of Europe, it makes sense to pay some attention”, says Pedro Narra Figueiredo. Speaking to CNN Portugal regarding the 50th anniversary of IPO Porto, Rui Henrique, director of this unit, even said that this “incidence [no Norte] turns out to be one of the largest in the world.”
In this specific cancer, carrying out endoscopies could have an “effective and beneficial cost”, and could be associated with colorectal cancer screening colonoscopy, says doctor Diogo Libânico, explaining that the high quality endoscopies that are already carried out in Portugal will be able to detect early tumors that can be treated, “avoiding surgeries” and even reducing the mortality rate.
The Research Center of the Portuguese Institute of Oncology (IPO) in Porto is developing tools for the early detection of gastric and colorectal cancer through the TOGAS project. Diogo Libânio cannot “estimate with certainty” how many new stomach cancers could be found early with the inclusion of this screening, but he tells us about Asian countries as a good example: “In countries without screening, the rate of early cancers is around 5 -10%, in Asian countries with screening the early cancer rate is 50%.”
Pedro Narra Figueiredo considers that screening should be aimed at “people with risk factors and stomach injuries”, pointing out that “there are studies that support that it is worthwhile, from the point of view of people’s health, to carry out screening with digestive endoscopy discharge linked to bowel cancer screening.”
As for the detection examination of Helicobacter pylorithere is already an infection detection program taking place on Terceira Island, in the Azores, but the president of the Portuguese Society of Gastroenterology says that the test does not have to be widespread, but should begin to be implemented more quickly in “people with more over 65 years old and sudden symptoms” or in “people with symptoms of gastritis, poor digestion, pain at night and weight loss”.
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