A study by the International Agency for Research on Cancer (IARC) indicates that one in eight cancer cases worldwide in 2024 may stem from infections. This amounts to 2.3 million cases, about 12% of new cancer diagnoses that year. Five infections account for a significant portion of these cases. The findings suggest that better infection control could help reduce the global cancer burden.
Published in Lancet Oncology on September 28, the study equates this fraction to the same proportion as lung cancer cases in the U.S. Dr. Patrick Moore from the University of Pittsburgh mentioned that the IARC’s estimates might be conservative, implying the actual impact of infections on cancer is likely higher. He emphasized the role of geography in the significance of specific infections.
Financial cut-backs in HIV treatment could increase infectious cancer rates in sub-Saharan Africa. Meanwhile, expanding neonatal HBV vaccination in Asia might result in fewer liver cancer cases. Karl Munger from Tufts University noted that this estimate is lower than anticipated, as some analyses suggest infection-related cancers account for 15-20% of global cases. The proportion is lower in high-income countries.
Leading Infections Causing Cancer
The study identifies Helicobacter pylori (H. pylori), human papillomavirus (HPV), hepatitis B virus (HBV), Epstein–Barr virus (EBV), and hepatitis C virus (HCV) as leading infectious causes of cancer in 2024. H. pylori is linked to around 760,000 gastric cancer cases. HPV is associated with approximately 750,000 cases, predominantly cervical and other related cancers.
HBV is linked to about 360,000 cancer cases, mostly liver cancer. EBV associates with approximately 260,000 cases, largely nasopharyngeal, gastric cancers, and Hodgkin lymphoma. HCV connects to around 160,000 cases, primarily liver cancer.
The highest cancer incidences appear in Eastern Asia, Sub-Saharan Africa, Central and Eastern Europe, and South-East Asia. Eastern Asia faces a high burden from H. pylori and HBV, while Sub-Saharan Africa sees high HPV-related cancer rates and substantial infections from HIV and Kaposi sarcoma-associated herpesvirus (KSHV). These differences likely reflect infection prevalence, prevention and treatment access, and broader socio-economic conditions.
Dr. Shan-Lu Liu at The Ohio State University remarked that many cancers are potentially preventable through vaccination, infection control, and treatment, highlighting infection-related cancer as a global health equity issue.
Mechanisms of Infection-Induced Cancer
Dr. Gary Clifford of IARC explains that certain infections hijack cellular mechanisms managing the normal cell cycle to aid their replication, increasing mutated cell risk and potentially leading to cancer. Chronic inflammation and repeated tissue damage also contribute, causing DNA damage and abnormal growth.
Liu noted that each infection potentially leading to cancer has specific pathways, hence their association with different cancers. For many infectious diseases, the virus carries oncogenes that directly cause cancer when inserted into healthy cells under specific conditions, according to Moore.
Preventing Infection-Related Cancers
Clifford highlighted that many cancers caused by infections are preventable. Vaccination, testing, and treatment are essential in prevention efforts, making infectious cancers particularly actionable targets. However, these tools are often underutilized due to financial, social, and political barriers, especially in low- and middle-income countries.
Challenges include limited vaccination access, screening, and treatment for infections. Social stigma further complicates prevention, particularly for diseases like HPV and HIV. Financial constraints, insufficient political commitment, and unequal care access also affect prevention efforts.
Next Steps
IARC scientists urge policy-makers to prioritize scaling up proven interventions, including vaccination against HPV and HBV, testing and treatment for H. pylori, HBV, HCV, and HIV, and measures to prevent transmission. Liu suggests expanding vaccination, enhancing testing and treatment accessibility, and bolstering cancer screening in high-risk populations, especially in regions with significant infection-related cancer burdens.