Millions of Cancers Linked to Infections, Study Says

Over 2 million new cancer cases were attributable to infections globally in 2024, according to an analysis of worldwide cancer incidence, highlighting the importance of effective prevention measures.

Infections led to an estimated 2.3 million new cancer cases in 2024, including gastric cancer, cervical cancer, hepatocellular carcinoma, leukemias and lymphomas, and nasopharyngeal cancer, which accounted for 12% of all cancer cases worldwide.

Among 12 carcinogenic infectious agents, the largest numbers of cancer cases were attributable to:

• Helicobacter pylori: 760,000 cases, population-attributable fraction (PAF) 4%
• Human papillomavirus (HPV): 750,000 cases, PAF 4%
• Hepatitis B virus (HBV): 360,000 cases, PAF 2%
• Epstein-Barr virus (EBV): 260,000 cases, PAF 1%
• Hepatitis C virus (HCV): 160,000 cases, PAF <1%
• Kaposi’s sarcoma-associated herpesvirus (KSHV): 35,000 cases, PAF <1%

Most cancers attributable to H. pylori were non-cardia gastric cancers (700,000 cases), while cervical cancer accounted for most HPV-attributable cases (600,000). HBV and HCV were responsible for 330,000 and 130,000 cases of hepatocellular carcinoma, respectively, while EBV led to 110,000 nasopharyngeal cancers, reported Harriet Rumgay, PhD, of the International Agency for Research on Cancer in Lyon, France, and colleagues in Lancet Oncology.

“Our findings underscore the importance of accelerating control of infectious agents to achieve cancer prevention goals,” Rumgay and colleagues wrote.

Clinicians can help reach those goals through interventions such as HBV and HPV vaccination; testing and treatment for H. pylori, HBV, HCV, and HIV; and cervical screening programs, Rumgay told MedPage Today.

Given those interventions, four of the five leading infectious causes of cancer, as well as HIV, already have “highly effective” prevention measures, she noted. Other measures can reduce transmission, such as safe injection practices, condom use, and HIV pre-exposure prophylaxis.

The challenge lies in the infections that currently have no effective prevention tools, particularly EBV, Rumgay said.

“A major priority is the development of vaccines against EBV, which causes several cancers and has also been linked to multiple sclerosis,” she explained. New prevention tools are also needed for KSHV, particularly given that the KSHV-related cancer burden falls disproportionately on resource-limited countries in sub-Saharan Africa.

Geography and infection prevalence present their own obstacles to taming infection-driven cancers, Rumgay added.

For example, eastern Asia accounted for 42% of infection-attributable cancers in 2024, while sub-Saharan Africa was responsible for 25% of cases. In eastern Asia, H. pylori and HBV infections were behind a majority of cancer cases, while HPV was the biggest cause in sub-Saharan Africa.

Given regional variations in infection prevalence, healthcare infrastructure, vaccination coverage, and screening and treatment, “there is no single prevention strategy that will work equally well everywhere,” Rumgay said. “As a result, prevention strategies need to be tailored to local infection and disease patterns and healthcare needs, while ensuring equitable access to effective interventions.”

Rumgay and colleagues analyzed 2024 national estimates of new cancer cases in people of any age from the Global Cancer Observatory’s Cancer Today database and other registry data. They estimated the percentages of cases that could be attributed to 12 infectious agents classified as Group 1 carcinogens by the International Agency for Research on Cancer Monographs Program.

For all cancers in 2024, the age-standardized incidence rate (ASIR) for cases caused by infectious agents was 22.7 cancer cases per 100,000 person-years. HPV had the highest ASIR, at 7.7 cases, followed by H. pylori (6.9), HBV (3.4), EBV (2.6), HCV (1.5), and KSHV (0.4).

The share of new cancer cases driven by infectious agents varied by region. Sub-Saharan Africa had the highest PAF, at 25%, followed by northern Africa (16%), southeastern Asia (16%), eastern Asia (15%), and the Caribbean and Central America (13%). In contrast, northern Europe (4%), and Oceania, North America, and western Europe (all 5%), were well below the 12% global PAF.

Study limitations included the lack of sex-specific PAFs, which may overlook sex-related differences in the percentages of infection-attributable cancer cases.