Half of cancer deaths in the world are due to preventable risk factors

Most cases of cancer are caused by avoidable factors. As the oncologist Josep Tabernero told EL PAÍS in 2017, “40% of tumors could be reduced by changing habits.” And he wasn’t on the wrong track. An international study published this Thursday in the journal The Lancet demonstrates the real impact of these carcinogens: in 2019, almost half of the deaths from cancer –a total of 4.45 million– were due to avoidable risk factors, such as tobacco, alcohol, obesity, pollution, unhealthy diets or occupational exposure to harmful elements such as asbestos, among others. A few months ago, another oncologist, Frenchman Thierry Philip, pointed out a key target: “If Europeans under 20 years of age stopped smoking tomorrow, cancer mortality would be halved in 50 years.”

The researchers reviewed data from the Global Burden of Disease, Injury, and Risk Factor (GBD) Study, which looks at 369 causes of death and disability and 87 risk factors for 204 countries and territories. Specifically, they focused on studying the impact of 34 risk factors on deaths and poor health from 23 types of cancer. They found that these risk factors explain 44.4% of cancer deaths in the world. Half of all male deaths from cancer, and more than a third in women, stem from these potentially preventable elements.

There are environmental risk factors, such as pollution; behavioral, such as smoking, drinking alcohol, or having unsafe sex; and metabolic, such as high body mass index or high blood glucose levels. But in the spotlight is tobacco, which fuels the appearance of up to 16 types of cancer. It is the clearest risk factor, lightyears ahead of the second, alcohol, and the third, high body mass index. To see the impact of each of them, the researchers used the disability-adjusted life years (DALY) indicator, which measures the global burden of disease and expresses the years lost due to illness, disability or early death. The age-standardized DALY rate for tobacco was 677.3 years lost per 100,000 population/year, while the rate for alcohol was 155 and for high body mass index 134.

The researchers also found differences between men and women. Men are more exposed to these risk factors. There was a disparity in DALYs attributed to smoking and alcohol consumption, much higher in men, “which could be due to greater exposure to these behavioral risk factors among men than among women,” the authors explain. Likewise, the disability-adjusted life years attributable to carcinogens at work were also higher. That could indicate, the researchers add, “that men are more likely than women to be employed in workplaces with high risk of exposure to carcinogens.

A boom in metabolic risks

Despite the fact that these risk factors are well known to oncologists and citizens, research warns that deaths associated with these preventable factors have increased by 20% in the last decade. And while tobacco continues to lead as the biggest driver of cancer, metabolic risks accounted for the largest percentage of increase in cancer deaths and ill health, with deaths increasing by 34.7%.

The weight of metabolic factors grows along with obesity and overweight rates, which have skyrocketed in the last 20 years. According to the data repository Our World in Data, excess fat has gone from being the cause of two million deaths in 1990 to five million in 2019. The scientific community has also warned that unhealthy diets and sedentary lifestyles that lead to obesity continue to rise, as do overweight levels in adults and children. An investigation by the Hospital del Mar Medical Research Institute (IMIM) in Barcelona concluded in 2019 that eight out of 10 men and 55% of women will be overweight or obese in 2030.

The situation varies greatly by country. But the highest burden of disease is in the most developed nations. Despite having more access to diagnosis, better treatments and higher survival rates, it makes perfect sense that the burden of this disease falls on rich countries, explains Esteve Fernández, director of Cancer Epidemiology, Prevention and Control at the Catalan Institute of Oncology: “Cancer is a chronic disease typical of developed countries, and it is where developing countries are headed. As a country grows, it evolves from a pattern of infectious diseases to a pattern of chronic diseases.”

The new study indicates that middle-income and low-income countries are in an “epidemiological transition.” Cancer-related death has increased in low-middle income countries in the last decade. “The increased burden of cancer attributable to metabolic risk could be the result of these countries undergoing an epidemiological transition, in which improvements in country-level development status are related to rising levels of obesity,” researchers suggest in the article.

The age-adjusted DALY ratio for environmental and occupational factors, such as exposure to pollution or carcinogens such as asbestos, cadmium or chromium, is skyrocketing in China and most of Europe. The DALY rate for behavioral factors, such as tobacco, alcohol or unhealthy diets, is lowest in Scandinavian countries. The weight of metabolic risks, meanwhile, is greatest in the United States, parts of Latin America, the United Kingdom and Eastern Europe.

Preventable deaths

Rodríguez assures that the study is “of high quality.” “It tells us indirectly what the avoidable deaths are. Forty-five percent of cancer deaths depend on risk factors that we could modify and, therefore, avoid.” The other half of deaths, adds Rodríguez, point to other causes: from genetic inheritance to other non-preventable risk factors, such as aging. In fact, the researchers themselves point out in the article that the risk factors included in the study “are based on knowledge of cancer risk factors, but as knowledge expands, there may be additional important risk factors to incorporate.” “In addition, there are known risk factors for cancer, such as exposure to sunlight and infectious agents, such as Helicobacter pylori,” they add.

The researchers point to the need for “more political commitment” to encourage health policies to prevent cancer. “Globally, there has been substantial progress in reducing tobacco exposure that can be linked to coordinated national and international prevention efforts. Interventions through tax and regulatory policies for tobacco use, including smoke-free policies, increased tobacco taxes, and advertising bans (...) have played an important role in these efforts. Similar efforts, including taxes and advertising bans, have been recommended to help reduce the harmful use of alcohol.”

Fernández assures that there is still a long way to go to prevent tobacco-related deaths. “Its impact is between four and five times higher than the rest of the factors. The sad thing is that we do nothing, and the worst thing is that you know what policies work, but the governments do not implement them. There is a gap between what we know works and what is put into practice. Smoke-free legislation works well because it protects non-smokers and makes smokers think about it. We also know that raising the price decreases the purchase of tobacco, as well as controlling advertising or making plain packaging. They are cheap measures,” argues the expert, who also proposes increasing taxes on sugary drinks and removing vending machines with unhealthy products from schools.