Increase in certain infections linked to subsequent cancer diagnosis
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Increased rates of certain infections, such as influenza, gastroenteritis, hepatitis and pneumonia, appeared associated with an eventual cancer diagnosis, according to research published in Cancer Immunology Research.
“Cancer can develop in an inflammatory environment caused by infections, immunity disruption, exposure to chemical carcinogens, or chronic or genetic conditions,” Shinako Inaida, PhD, visiting researcher at Graduate School of Medicine at Kyoto University in Japan, said in a press release. “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. This information may contribute to reports to prevent or detect cancer.”
Inaida and colleagues conducted a 7-year, case-control study using data from a medical claims database in Japan to determine the annual rate of infections among adults aged 30 years and older with no previously known immunodeficiencies. Cases included 2,354 patients (median age, 45.1 years; 78.3% men) diagnosed with cancer between July of 2010 and June of 2011. Controls included 48,395 individuals (median age, 43.9 years; 78.1% men) who were cancer free between 2005 and 2012.
Researchers calculated and compared annual prevalence rates for influenza, gastroenteritis, hepatitis and pneumonia infections between controls and cases.
The most common cancer types among cases included digestive/gastrointestinal (n = 583), head and neck (n = 399) and stomach (n= 346). Other cancer types included respiratory/thoracic (n = 288), germ cell (n = 271), genitourinary (n = 182), liver (n = 99), breast (n = 60), hematologic/blood/bone/bone marrow (n = 41), endocrine (n = 30) and unknown/other (n = 55).
Researchers observed higher rates of infection among cases during the 6 years before a cancer diagnosis compared with controls during the same time period.
Age-adjusted odds for infection in the case group increased annually, from a 16% higher likelihood compared with controls during the first year to a 55% higher likelihood during year 6.
The largest difference in annual prevalence rates occurred during year 6 — 1 year before a cancer diagnosis. Compared with controls, infection prevalence rates for cases were 18% higher for influenza, 46.1% for gastroenteritis, 232.1% for hepatitis and 135.9% for pneumonia.
Researchers reported the highest age-adjusted OR for hepatitis infection, with cases having a 238% higher likelihood for hepatitis compared with controls.
Moreover, researchers found that certain infections appeared associated with certain cancer types. For example, the OR for influenza infection within a year of cancer diagnosis was highest among those with male germ cell cancers (OR = 2.01; 95% CI, 1.31-3.09); the OR for pneumonia was highest among those who went on to develop stomach cancer (OR = 3.59; 95% CI, 2.04-6.3); and the OR for hepatitis infection was highest among those who developed hematologic, blood, bone or bone marrow cancers (OR = 19.04; 95% CI, 4.55-79.67).
Study limitations included a lack of information about environmental exposures, lifestyles or underlying genetic or medical conditions that could have contributed to increased infection in addition to causing cancer.
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