Yet Another Consequence of Getting COVID

If you've had cancer, do you really want to take further chances? 

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From MedPage Today 7/30/25:

COVID Infection May Ignite Dormant Cancer in Survivors, Study Says; These patients should consider vaccination against respiratory viruses, according to researcher

by Mike Bassett, Staff Writer

"Common respiratory infections such as COVID-19 and the flu may be able to awaken dormant breast cancer cells that have spread to the lungs and promote the development of new metastatic tumors, researchers suggested.

"Using findings from a mouse model, this conclusion was corroborated with observational data in humans that showed increases in death and metastatic lung disease among cancer survivors infected with SARS-CoV-2, reported James DeGregori, PhD, of the University of Colorado Cancer Center in Aurora, and colleagues in Natureopens in a new tab or window.

"Focusing on cancer survivors in the U.K. Biobank who had been diagnosed at least 5 years before the COVID pandemic, the team found that after excluding survivors who died from COVID, those who tested positive for COVID had an almost two-fold higher risk of dying from cancer compared with patients with cancer who had tested negative (OR 1.85, 95% CI 1.14-3.02).

"When they reduced the follow-up period from January 2022 to December 2020, the OR increased to 8.24 (95% CI 3.43-19.77), indicating "that the increased risk of cancer mortality is greatest in the first few months after SARS-CoV-2 infection."

"The authors then looked at 36,845 women with breast cancer from the Flatiron Health database to specifically determine whether they had an increased risk of progression to metastatic disease in the lungs after COVID infection. They found that survivors who had COVID after their initial breast cancer diagnosis showed an age-, race-, and ethnicity-adjusted hazard ratio of 1.44 (95% CI 1.01-2.05, P=0.043) for subsequent diagnosis of metastatic breast cancer in the lungs.

"Our findings indicate that individuals with a history of cancer may benefit from taking precautions against respiratory viruses, such as vaccination when available, and discussing any concerns with their healthcare providers," said co-author Julio Aguirre-Ghiso, PhD, of the Montefiore Einstein Comprehensive Cancer Center in the Bronx, New York, in a press release.

"We don't want to scare people -- it's one study and more needs to be done," DeGregori told MedPage Today. "But, I think it would be reasonable to conclude that avoiding infection would be a good idea -- which is a good idea anyway. And these respiratory viruses are still very relevant. Even though the COVID-19 pandemic has subsided, COVID is certainly here to stay, and there are likely to be future coronaviruses that cause disease."

"The researchers noted that prior evidence has suggested that inflammatory processes can awaken disseminated cancer cells (DCCs) -- cells that break away from a primary tumor and spread to distant organs.

"And if there is anything that is inflammatory, it is a respiratory virus, such as COVID-19," DeGregori said. "So we specifically set out to test whether respiratory virus infections might lead to an awakening of these cancer cells, leading to metastatic progression of the disease."

"He and his team tested this hypothesis by using a unique mouse model of metastatic breast cancer, which included dormant DCCs in the lungs, and then exposing the mice to SARS-CoV-2 or influenza.

"And the results were really dramatic," DeGregori said. "We saw a massive awakening -- a 100- to a 1,000-fold increase in the burden of these cancer cells in the mice after infection over a few-week period."

"In attempting to understand the mechanism of this process, the researchers conducted a molecular analysis that demonstrated that the awakening of these dormant DCCs was driven by interleukin-6 (IL-6), a protein that immune cells release in response to injuries or infection.

"We showed that without IL-6, these cancer cells would not awaken nearly to the same extent," DeGregori explained.

"The team also found that this process is followed "by a return to quiescence and establishment of CD4+ cell niches that inhibit DCC elimination, partly through the suppression of CD8+ cells."

"In other words, "once these cells have expanded, they are actually protected by the immune system," DeGregori said. "Instead of the immune system actively eliminating the cancer cells, it protects them from immune elimination. We need to better understand this mechanism of immune suppression so that perhaps we can reverse it and allow the immune system to better control the cancer."

"While acknowledging that species differences "warrant caution in interpreting mouse data," DeGregori and colleagues concluded that the population-based data "show that COVID-19 increases lung metastasis risk in female patients with breast cancer.""