Modifiable risk factors account for almost 40% of the worldwide cancer burden, according to an international study group that said smoking, infections and alcohol consumption topped the list of 30 mostly behavioural factors, reports MedPage Today.
Based on data from 2022, the report showed that an estimated 37.8% of the 18.7m cancers were attributable to these factors, 29.7% for women and 45.4% for men. Rates of cancers associated with modifiable risk factors varied by geography, ranging as high as 38.2% in women and 57.2% in men.
Smoking, infections, and alcohol consumption topped the list, accounting for 28.5% of the worldwide cancer burden.
A breakdown by site of cancer showed that lung, stomach and cervical cancers accounted for almost half of all potentially preventable cancers, and the predominant modifiable factors associated with those three cancers were smoking, Helicobacter pylori infection and human papillomavirus infection, respectively.
Other cancers cited in men included liver and colorectal cancers, with the predominant modifiable factors there including infection, smoking, alcohol and high body mass index (BMI).
The report was published in Nature Medicine this week, ahead of World Cancer Day (4 February), and discussed during a press briefing by representatives of the World Health Organisation (WHO) and the International Agency for Research on Cancer (IARC), which supported the study.
“What’s important to note is that even in regions with lower proportions, the number of absolute cancer cases that can be prevented remains substantial, which is why prevention strategies are universally relevant,” said Isabelle Soerjomataram, MD, of the IARC Cancer Surveillance Branch in Lyon, France.
The investigators found male/female differences particularly striking.
“Smoking dominates as the leading preventable cause for men, ranking as the most important cause of cancer in 126 of the 185 countries included in the study,” she said. “For women, infections lead. It is the most important process, ranking first in 141 countries out of 185.
This striking difference reflects distinct epidemiological patterns, cultural and social norms, and underscores why tailored prevention strategies are essential to reduce the burden of cancer."
“A one-size-fits-all global prevention strategy is not sufficient,” Soerjomataram added. “Each country and region needs to adapt global and regional strategies to prevention priorities that are aligned with its specific cancer burden profile.”
Report co-author Andre Ilbawi, MD, team leader for cancer control at WHO, emphasised the humanistic side of the data.
“A cancer diagnosis is life-changing, yet experiences differ sharply between and within countries,” he said. “For a privileged few, access and innovation are driving survival rates beyond 70%, but for far too many, cancer remains a death sentence, often compounded by devastating social and financial hardships.
“Today, we are here to celebrate good news, founded on strong science: many cancers are preventable. Our new findings … can help us understand what is driving the cancer burden and the highest risks for different populations.”
He noted that the risk factors identified in the study place a massive strain on health systems through many other diseases. “Investing in cancer prevention, therefore, delivers wide-ranging health, societal, and economic benefits,” he said.
Communication surrounding modifiable risk factors should “keep the focus on risk reduction, not blame”, he added. “Guilt and blame, for people affected by cancer, harm mental health, delay care, and reduce quality of life.”
Spotlight on variations
Cancer incidence attributable to a modifiable risk factor hinges on the prevalence of a risk factor within a specific population, said Farhad Islami, MD, PhD, of the American Cancer Society in Atlanta. High BMI, or obesity, offers an example that distinguishes the US from the global prevalence of modifiable risk factors.
“The proportion of cancers attributable to high BMI (in this analysis) is higher in North America, more than double the proportion globally (5.2% vs 2.4%) … because high BMI is more common in North America,” Islami told MedPage Today.
“The estimate for North America is closer to the American Cancer Society’s estimate (7.6%), but some differences between these two estimates are expected, because the ACS estimate is for the US only, but estimates in the recent study for North America also includes Canada and Mexico, with lower prevalence of high BMI than in the United States."
“The opposite is true for cancers attributable to infections,” he observed. “In some countries, cancers attributable to infections … are much more common than in the United States. The cancer burden attributable to infections is much lower in North America than globally (4% and 10.2% among women, for example) or some other regions (e.g, 24.3% in sub-Saharan Africa).”
The most recent Global Burden of Disease showed that 44% of global cancer deaths could be attributed to modifiable risk factors. However, the estimate did not include infectious disease, which is a major contributor to cancer risk, authors of the WHO/IARC report noted.
Most previous studies of cancer and risk attribution focused on mortality, providing a rationale to investigate the impact of modifiable factors on cancer incidence.
Investigators examined associations between cancer and 30 modifiable factors:
Smoking
Alcohol consumption
Obesity (high BMI)
Insufficient physical activity
Smokeless tobacco and areca nut
Suboptimal breastfeeding
Air pollution
Ultraviolet radiation
Infection (nine agents)
Occupational exposures (13 agents)
Key findings
GLOBOCAN data for 2022 showed 20m new cases of cancer worldwide and about 10m deaths. Overall, 7.1m cancers were attributable to modifiable risk factors, including 2.7m of 9.2m total cancers in women and 4.3m of 9.6m cancers in men.
Infection and smoking were the top contributors among women (cervical and lung cancers), whereas any tobacco use and infections were the leading modifiable factors in men (lung, stomach, and liver).
Contributions of individual risk factors varied more in women than in men and exhibited distinct regional patterns. Overall, infections were the leading contributor in 141 countries, followed by infections in 38 and high BMI in six. Infections accounted for the most new cancers in sub-Saharan Africa (30.3%), South-Central Asia (18.1%), and Southeast Asia (16.7%).
In contrast, smoking predominated in Northern Europe (12.5%), North America (12.2%), and Western Europe (10.6%)
Among men, smoking was the predominant contributor in 126 of the 185 countries, followed by infections in 58 countries. Globally, smoking contributed to 23.1% of all new cancers, followed by infections (9.1%), and alcohol consumption (4.6%).
Lung cancer led the way in women and men with regard to preventable cancers. In women, 60.5% of 477 869 new lung cancers were attributable to smoking, followed by air pollution (27.5%) and occupational exposures (12%).
More than twice as many lung cancers occurred in men (1.3m), 69.4% attributable to smoking, 15.8% to air pollution, and 14.7% to occupational exposures.
“Ultimately, our results reinforce the call for effective cancer prevention, which requires sustained political commitment and investment tailored to the specific risk profiles of populations worldwide,’ the authors concluded.
See more from MedicalBrief archives:
Widespread ignorance of links between diet and cancer — World Cancer Research Fund
Alcohol consumption linked to rising cancer cases – US study
400 UK cancer cases daily from junk food, alcohol and sunbathing