A recent study published in The Lancet Oncology has found that approximately 12% of the world's total cancer cases in 2024 were likely caused by infections. The research, conducted by the World Health Organization, analyzed the frequency and causes of different cancers, focusing on the role of infections. The study linked 2.3 million new cancer cases to infections, primarily caused by five pathogens: Helicobacter pylori, human papillomavirus, hepatitis B, Epstein-Barr virus, and hepatitis C.
These infections can cause over 20 different types of cancer, including stomach, liver, blood, and cervical cancers. The study's authors have been researching this field for around thirty years, with previous work investigating cancer cases caused by infections in 1990, 2002, 2008, 2012, and 2018. Although the proportion of cancer cases caused by infections may appear to have dropped during those years, the authors stress that comparisons cannot be made confidently due to changes in data sources and quality.
The study aims to highlight where controlling and preventing infections can help reduce cancer rates. Infections can cause cancer through various molecular mechanisms. Viruses can directly or indirectly change the genes of the host cell, making it more likely to grow out of control and become cancerous. There are three main ways viruses can do this: by turning off the cell's ability to destroy itself, inserting their DNA into the host cell's DNA, or carrying a gene that causes cancer.
Bacteria and parasites, such as Helicobacter pylori and Opisthorchis viverrini, can also lead to cancer, but work more indirectly. Chronic infection by these organisms can cause significant stress to tissues, leading to overactive inflammation and DNA damage. This can result in genetic mutations that put cells on the road to becoming cancerous. The link between infections and cancer is foundational to modern cancer science and has helped scientists uncover the direct link between genetics and cancer.
The study's findings reinforce that many cancers are preventable. In Australia, the human papillomavirus vaccine has been successful in reducing HPV infections by 90% among eligible individuals since its introduction in 2007. However, vaccination rates among 15-year-olds have fallen from 85.7% in 2020 to 79.5% in 2024, which is concerning. The WHO and Australian target is to vaccinate 90% of 15-year-old girls by 2030.
The study also highlights that around 75% of cancers caused by infections were found in low- and middle-income countries. Treating infections that can lead to cancer, such as HIV, H. pylori, and hepatitis B and C, is one way to reduce cancer rates. Preventative measures, including vaccinations, condoms, and disease screening, also play a major role. However, access to these programs in poorer countries can be limited, making it a significant equity issue in combating cancer.
The research emphasizes the importance of controlling and preventing infections to reduce cancer rates globally. By understanding the molecular mechanisms behind the link between infections and cancer, scientists can develop effective strategies for prevention and treatment. The study's findings have significant implications for public health policy, particularly in low- and middle-income countries where access to preventative measures and treatments can be limited.
Key points
- Around 12% of global cancer cases in 2024 were likely caused by infections.
- Five pathogens - Helicobacter pylori, human papillomavirus, hepatitis B, Epstein-Barr virus, and hepatitis C - were primarily responsible for the infections.
- Many cancers caused by infections are preventable through vaccination, treatment, and preventative measures.
