Infections Linked to Global Cancer Cases

In 2024, one in eight global cancer cases were attributed to infections, according to the International Agency for Research on Cancer (IARC). This translates to 2.3 million new cancer cases or about 12 percent of cases that year. Five specific infections were responsible for a substantial portion of these cases.

The IARC study suggests that a significant part of the global cancer burden could be avoided through improved infection control strategies. The findings, highlighted in the Lancet Oncology journal on September 28, stress that infections are a critical factor in cancer development. Dr. Patrick Moore from the University of Pittsburgh emphasized that infections are as influential as lung cancer among U.S. cancer patients.

The study estimates might be conservative, indicating the real impact of infections on cancer prevalence could be even larger.

Dr. Moore also noted that geographical factors influence infection-related cancer cases. In regions where HIV treatment funding declines, such as in sub-Saharan Africa, infection-related cancers could rise. Conversely, in Asia, increased neonatal HBV vaccination might reduce liver cancer cases.

Professor Karl Munger from Tufts University shared that the IARC’s estimate is lower than expected. Other analyses suggest infection-associated cancers account for 15 to 20 percent of global cancer cases but are less prevalent in high-income countries.

The Major Infections

The study identified the leading infectious causes of cancer in 2024:

• Helicobacter pylori (H. pylori): 760,000 gastric/stomach cancer cases globally.
• Human papillomavirus (HPV): 750,000 cases, mainly cervical, anal, vulvar, vaginal, penile, and some head and neck cancers.
• Hepatitis B virus (HBV): 360,000 cases, primarily liver cancer.
• Epstein–Barr virus (EBV): 260,000 cases, linked to nasopharyngeal cancer, some gastric cancers, and Hodgkin lymphoma.
• Hepatitis C virus (HCV): 160,000 cases, predominantly liver cancer.

Regional differences in infection prevalence and access to healthcare contribute to cancer case disparities. Eastern Asia grapples heavily with H. pylori and HBV, while sub-Saharan Africa faces high HPV-related cancer rates alongside infections like HIV.

Mechanisms of Infection-Induced Cancer

Dr. Gary Clifford from the IARC explained that infections often manipulate cellular processes for replication. This can interfere with gene repair or cell death mechanisms, raising cancer risks. Chronic inflammation and repetitive tissue damage also increase DNA damage, aiding abnormal cell growth.

Dr. Liu described varied mechanisms through which infections can promote cancer. Each infection tends to result in specific cancer types due to distinct mechanisms at play.

At least five infections carry oncogenes capable of directly triggering cancer when introduced into healthy cells.

These oncogenes spur cell proliferation under factors like immune suppression.

Prevention Potential

The study indicates many infection-induced cancer cases are preventable. Infection-related cancer prevention more feasible than those stemming from lifestyle factors, owing to the ability to vaccinate, test, and treat the underlying infections.

Yet, current prevention tools, like HPV and HBV vaccines, are often underused or inaccessible, especially in low- and middle-income countries.

Key challenges include limited access to vaccination, screening, and treatment amid financial, social, and political barriers. Prevention programs often suffer from lack of funds and insufficient political support.

The Way Forward

IARC researchers urge scaling up interventions like HPV and HBV vaccination, screening, and treatment for infections such as H. pylori and HIV. Strengthening these efforts among high-risk populations and increasing access in regions with heavy infection-related cancer burdens is vital.

Efforts should focus on improving vaccination coverage, enhancing infection treatment accessibility, and reinforcing cancer screening initiatives for vulnerable communities.

These measures, paired with addressing socio-economic factors, can potentially reduce global cancer cases linked to infections.