Respiratory infections like COVID-19 and the flu can activate dormant cancer cells in breast cancer patients who are in remission, new research finds.
The study, published in Nature, found that common viruses can reawaken small numbers of dormant breast cancer cells in the lungs.
Researchers began investigating the link after the team noticed that U.K. patients who were in remission from breast cancer and tested positive for COVID later showed a two-fold increase in cancer-related deaths.
They also analyzed a U.S. database that included nearly 37,000 patients and found that COVID infection was associated with a more than 40 percent increased risk of metastatic breast cancer in the lungs.
Studies on mice found that influenza and COVID infections triggered dormant breast cancer cells after just days of infection. Within two weeks, researchers observed “massive expansion” of the cancer cells into metastatic lesions by more than 100 times.
Scientists have suspected that common viruses like Epstein-Barr can trigger some cancers. Human papillomavirus (HPV) is already documented to trigger cervical cancer.
When it comes to breast cancer, however, research on human cells was limited, and it’s not entirely known how the virus triggers the disease to spread.
The findings suggest the body’s immune response plays a role.
After breast cancer goes into remission, a tiny number of cells remain dormant in lung, bone and liver tissue. Sometimes, inflammation can wake up the cells.
In the mouse experiments, both influenza A and coronavirus only reawakened dormant cells if they triggered an inflammatory cytokine response.
More research is needed to see if vaccination makes a difference when it comes to the possibility of reawakening dormant cells.
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