Covid & Flu Viruses May Awaken Dormant Breast Cancer Cells In Lungs: Study

A recent study has revealed that common respiratory viruses, including COVID-19 and influenza, may trigger dormant breast cancer cells in the lungs to become active again, potentially leading to the formation of new metastatic tumours.

The research, published in Nature, was conducted by scientists from the Albert Einstein College of Medicine in the US and Utrecht University in the Netherlands.

The study builds on previous evidence suggesting that severe inflammation—such as that caused by respiratory infections—can awaken disseminated cancer cells (DCCs).

These cells, which had spread from the original breast tumour to distant sites such as the lungs, often remain dormant for years.

However, infections that induce strong immune responses may create an environment in which these cells can reactivate and multiply.

During the pandemic, a rise in cancer-related deaths raised concerns that Covid-19 could be contributing to cancer recurrence. The latest findings support this concern.

Animal and Human Data Provide Insight

Using mouse models, researchers exposed dormant breast cancer cells in the lungs to either the influenza virus or SARS-CoV-2, the virus responsible for COVID-19.

Both viruses caused a rapid awakening and proliferation of the cancer cells. Within days, there was a marked increase in metastatic activity, and visible lung lesions appeared within two weeks.

At the molecular level, the team identified interleukin-6 (IL-6)—an inflammatory protein produced during immune responses—as a key driver of this reactivation.

This discovery opens potential pathways for using IL-6 inhibitors or other immunotherapies to prevent metastatic relapse.

To understand the relevance in human patients, researchers analysed two large databases of cancer survivors.

The results showed a clear link between respiratory infections and an increased risk of cancer metastasis, particularly in the first year after infection.

“Our findings indicate that individuals with a history of cancer may benefit from taking precautions against respiratory viruses, such as vaccination when available,” said lead researcher Julio Aguirre-Ghiso.

Professor Roel Vermeulen, co-author from Utrecht University, added, “The findings highlight the critical need for monitoring cancer survivors following infections, especially before the availability of COVID-19 vaccines.”

This research underlines the importance of protecting cancer survivors from respiratory illnesses, not only to prevent infection but also to potentially avoid cancer recurrence.

Future studies may focus on how targeted therapies can mitigate this newly uncovered risk.

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