Can Increased Rate of Infections Predict Cancer?

Findings from a recent study suggest that patients may experience a greater occurrence of infections in the years preceding a cancer diagnosis. 

Infections and cancer

Inflammation is an immune reaction that may lead to the development of cancer. Inflammation can develop in response to infection, exposure to chemical carcinogens, chronic genetic conditions, or other factors. 

As a result, researchers think the status of an individual’s immune system may be a factor in the development of cancer. Additional research is needed, however, to understand the relationship between precancerous immunity, infections, and cancer development. 

Shinako Inaida, PhD, a visiting researcher at the Graduate School of Medicine at Kyoto University in Japan, and Shigeo Matsuno, PhD, examined a medical claims database in Japan to determine the annual rate of infections in adults from 2005 to 2012. The study was published in Cancer Immunology Research, a journal of the American Association for Cancer Research,  

Dr. Inaida and Dr. Matsuno compared individuals who were diagnosed with any malignant cancer between July 2010 and June 2011 (the case group) with individuals who were not diagnosed with cancer between January 2005 and December 2012 (the control group). 

The annual prevalence rates for influenza, gastroenteritis, hepatitis, and pneumonia infections were calculated for each group. The authors found that individuals who were diagnosed with cancer had experienced higher rates of infection over the six years prior to their cancer diagnoses than those without a cancer diagnosis. 

The largest differences in annual infection prevalence rates occurred in the sixth year – the year before a diagnosis. During that year, the infection prevalence rates for the case group were significantly 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 odds of infection increased each year leading up to their cancer diagnosis. 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 hepatitis infection were highest in those who were later diagnosed with blood, bone, or bone marrow cancers. The odds of contracting the flu just before cancer detection were highest for those who developed testicular cancer. The odds of pneumonia were highest in those who went on to develop stomach cancer. 

“Interestingly, we found that infection afflicting a specific organ did not necessarily correlate with increased risk of cancer in the same organ,” noted Dr. Inaida.

Together, the results of this study indicate that a higher occurrence of infections may precede a cancer diagnosis. Additional research is needed to understand whether precancerous changes increase susceptibility to infection, or if having a greater number of infections promotes cancer development.