“This is a very important study for several reasons,” Anton Bilchik, MD, PhD, a surgical oncologist, chief of medicine and Director of the Gastrointestinal and Hepatobiliary Program at Providence Saint John’s Cancer Institute in Santa Monica, CA, who was not involved in the research, told Medical News Today.

Bilchik emphasized the importance of this research, given that “cancer is a global problem and a major cause of mortality, up to 40% of cancers are preventable through lifestyle modification, nutrition, environmental exposure and vaccination and lower socioeconomic countries have a disproportionate increase in preventable cancers.”

The IARC team that conducted the analysis examined data from 185 countries, taking into account 36 cancer types, including breast, lung, colorectal, cervical cancer, stomach cancer, leukemia, and skin cancer (melanoma).

The researchers found notable differences in the spread of preventable cancers on a global level.

The IARC considered a wide array of modifiable risk factors, including smoking (tobacco use), alcohol consumption, body mass index (BMI), a sedentary lifestyle, air pollution, and exposure to ultraviolet radiation.

Additionally, for the first time ever, the researchers accounted for the impact of nine viral, bacterial, and parasitic infections linked to different forms of cancer. The infectious agents the team looked at were:

1. Helicobacter pylori, a bacterium that infects the stomach and can cause stomach and sometimes colorectal cancer
2. High-risk human papillomavirus (HPV), which includes types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59, and is linked to cervical cancer
3. The hepatitis B virus (HBV) and the hepatitis C virus (HCV), both of which affect the liver and are linked to liver cancer
4. The Epstein–Barr virus, which is linked to nasopharyngeal carcinoma, Burkitt lymphoma (a form of non-Hodgkin lymphoma), and Hodgkin’s lymphoma
5. The human herpes virus type (HHV-8), which can cause Kaposi sarcoma
6. Schistosoma haematobium, which causes a parasitic infection linked to bladder cancer
7. human T‑cell lymphotropic virus, which can be a risk factor for leukemia
8. Opisthorchis viverrini, which can cause a parasitic infection sometimes linked to cancer of the bile ducts
9. and Clonorchis sinensis, a foodborne pathogen likewise linked to bile duct cancer.

While all of these infections are preventable through vaccination and screening, access to these measures is limited in certain regions of the world.

“Infections account for a particularly large share of cancers in sub-Saharan Africa and parts of Asia, where high prevalence of HPV, H. pylori, HBV, HCV and other agents is sustained by limited access to vaccines, testing and screening, safe water and sanitation, and timely treatment,” study author Isabelle Soerjomataram, MD, PhD, Deputy Head of the Cancer Surveillance Unit (CSU) at the IARC, explained to MNT.

“The study highlights several effective [prevention] strategies [for cancers caused by infections]: scaling up HPV vaccination, implementing and maintaining HBV birth-dose vaccination and broader HBV/HCV control, and test‑and‑treat or eradication programmes for H. pylori in high risk settings,” added Soerjomataram.

The study points to smoking tobacco, infections, and alcohol consumption as the top three preventable risk factors for cancer globally.

Specifically, smoking was linked to a little over 15% (3.3 million) of all new preventable cancer cases globally, infections to over 10% (2.3 million cases), and alcohol use to more than 3% (700,000) of cases.

The most commonly diagnosed types of preventable cancers worldwide were lung, stomach, and cervical cancer. These were linked primarily to:

• smoking and air pollution (lung cancer)
• H. pylori infections (stomach cancer)
• and HPV infections (cervical cancer).

Commenting on the study findings, Bilchik told MNT that:

“Smoking is associated with many cancers but is the most common cause of lung cancer. In general, more men smoke than women, although in several countries the incidence of smoking is decreasing because of social awareness. HPV is a sexually transmitted virus and the most common cause of cervical cancer. HPV vaccination, which is extremely effective in prevention of cervical cancer, is recommended in all adolescent women but is disproportionately available in more affluent countries.”

One of the most striking findings of the analysis was that, overall, there were significantly higher rates of preventable cancers among men than among women.

More than 45% (or 4.3 million) of new cancer cases in men, globally, were linked to preventable causes, while modifiable risk factors accounted for approximately 30% (2.7 million) of new cases in women.

As to the causes, smoking was the highest risk factor for men, accounting for a little over 23% of all new cancer cases.

In women, infections were the most notable culprit, accounting for 11.5% of all new cancer cases.

“Overall, about 45.4% of cancers in men versus 29.7% in women are attributable to the included risk factors, with especially high fractions in men in East Asia and parts of Europe,” Soerjomataram told us.

The study author explained that:

“Men tend to have higher exposure to several major risks — notably tobacco smoking, alcohol, and some occupational carcinogens — and these factors drive high burdens of lung, stomach, liver, and colorectal cancers, whereas women’s risk profile is more diversified and variable between higher and lower income regions.”

However, she cautioned that “some determinants that are particularly relevant for women, including several reproductive and hormonal factors, are not captured in this analysis, so the proportion of cancers attributable to modifiable factors in women is likely underestimated.”

“Importantly, the findings reinforce the need for gender-responsive cancer prevention and research, ensuring that policies and interventions are designed and implemented in ways that address the distinct risk profiles and social contexts of women and men,” Soerjomataram added.

Advising on prevention strategies for cancer at the individual level, Bilchik said everyone can take concrete action right now to reduce their risk.