Increased Rate of Infections Correlated to Eventual Cancer Development

Patients experienced a greater occurrence of infections in the years preceding a cancer diagnosis, according to a paper published today in Cancer Immunology Research by researchers at Kyoto University.

"Cancer can develop in an inflammatory environment caused by infections, immunity disruption, exposure to chemical carcinogens, or chronic or genetic conditions," explained lead author Shinako Inaida. "An individual's immunity is thought to be a factor in the development of cancer, but additional research is needed to understand the relationship among precancerous immunity, infections, and cancer development," added Inaida. "This information may contribute to efforts to prevent or detect cancer."

Studies have suggested an increase in infections prior to the development of non-solid tumors, such as lymphoma, chronic lymphocytic leukemia, and myeloma. However, fewer studies have examined infection prior to the development of solid tumors.

In this retrospective case-control study, Inaida, along with Shigeo Matsuno examined a medical claims database in Japan to determine the annual rate of infections in adults from 2005 to 2012. Individuals 30 years of age and older without any recorded immunodeficiencies were included in the study. The case group was composed of 2,354 individuals, and the control group was composed of 48,395 individuals.

The authors found that individuals in the case group had experienced higher rates of infection over the six years prior to their cancer diagnoses than those in the control group over the same time period. The largest differences in annual infection prevalence rates occurred in the sixth year, which was one year prior to cancer diagnosis. During this year, the infection prevalence rates for the case group were higher than the control group by 18 percent for influenza, 46.1 percent for gastroenteritis, 232.1 percent for hepatitis, and 135.9 percent for pneumonia.

For individuals in the case group, the age-adjusted odds of infection increased each year. During the first year, those in the case group had a 16 percent higher likelihood of infection than the control group, compared with a 55 percent greater risk in the sixth year. During the sixth year, the highest age-adjusted odds ratio was observed for hepatitis infection, with those in the case group having had a 238 percent higher likelihood of hepatitis infection than those in the control group.

The authors also found that certain infections appeared to have a greater association with certain cancer types. The odds of influenza infection just before cancer detection, for example, were highest for those who developed male germ cell cancers. Additionally, the odds of pneumonia were highest in those who went on to develop stomach cancer, and the odds of hepatitis infection were highest in those who developed hematologic, blood, bone, or bone marrow cancers. "Interestingly, we found that infection afflicting a specific organ did not necessarily correlate with increased risk of cancer in the same organ," noted Inaida.