Health Affairs Can Covid-19 and Flu Viruses Trigger Breast Cancer Relapse? A New Study Raises Concerns
A recent study published in Nature has uncovered a potentially alarming link between common respiratory infections—like Covid-19 and influenza—and the reactivation of dormant breast cancer cells in the lungs.
According to researchers, these infections could awaken hidden cancer cells, leading to the formation of new metastatic tumors.
Dormant Cancer Cells: The Silent Threat
After treatment, many breast cancer patients carry dormant cancer cells (DCCs) that have spread to other parts of the body, particularly the lungs.
These cells can lie inactive for years, posing no immediate threat.
However, under certain conditions—such as severe inflammation—they can “wake up,” grow, and form new tumors.
The new study, conducted by scientists at the Albert Einstein College of Medicine, sheds light on how respiratory viruses may trigger this process.
“Our findings suggest that cancer survivors should take precautions against respiratory viruses,” said Dr. Julio Aguirre-Ghiso, the study’s lead author.
“This includes keeping up with vaccinations and consulting healthcare providers about their individual risks.”
What the Research Found
Researchers infected mice carrying dormant breast cancer cells with either SARS-CoV-2 (the virus behind Covid-19) or the influenza virus.
The result? A rapid reactivation of dormant cells in the lungs. Within just a few days, the number of metastatic cancer cells surged—and by two weeks, metastatic tumors had begun to form.
The culprit, scientists believe, is interleukin-6 (IL-6), a protein released by immune cells during infection. IL-6 triggers inflammation,
which in turn may activate dormant cancer cells. The study suggests that therapies targeting IL-6 or similar pathways could help prevent such metastasis.
Human Data Supports the Findings
In addition to the mouse experiments, researchers analyzed real-world patient data and found similar patterns.
Cancer survivors who experienced respiratory infections had a noticeably higher risk of metastatic relapse—especially within the first year of recovery.
Dr. Roel Vermeulen from Utrecht University, a co-author of the study, added:
“Even common respiratory infections could raise the risk of metastasis in cancer survivors.
It’s a red flag that needs more attention—especially since the study focused on the pre-vaccine period of the pandemic.”
Why This Matters
For millions of breast cancer survivors, this study is a critical reminder: staying vigilant about respiratory health isn’t just about avoiding the flu or Covid—it’s potentially about avoiding cancer recurrence.
While more research is needed, the message is clear—vaccination, masking during outbreaks, and open dialogue with healthcare providers may be more important than ever for cancer survivors.
Stay informed. Stay protected. And if you’re a cancer survivor, talk to your doctor about what steps you can take to lower your risk.
Can Covid-19 and Flu Viruses Trigger Breast Cancer Reactivation? What the Latest Research Shows
A groundbreaking study published in Nature (2024) has revealed surprising, potentially far-reaching implications
common respiratory infections like Covid-19 (SARS‑CoV‑2) and influenza may actually awaken dormant breast cancer cells in the lungs, leading to new metastatic tumors.
What Was Discovered in the Animal Studies
Researchers used mouse models bearing dormant disseminated cancer cells (DCCs) in the lungs.
After infecting them with either influenza or SARS‑CoV‑2, DCCs rapidly exited dormancy and began proliferating.
Within just a few days, cancer cell counts in the lungs increased up to 100-fold, and visible metastatic lesions emerged within two weeks.
Molecular analyses pinpointed interleukin‑6 (IL‑6), an inflammatory cytokine, as a key driver—released by immune cells in response to infection.
IL‑6 activates the JAK/STAT3 signaling pathway, triggering inflammation that flips dormant cells into active cancer proliferation.
Additional immune mechanisms—like T cell balance, neutrophil activity, and neutrophil extracellular traps—also play roles in triggering metastasis.
Supporting Evidence from Human Data
Analyses of clinical databases showed that cancer survivors who contracted SARS‑CoV‑2 had significantly higher risks of lung metastatic progression and cancer-related mortality.
compared to survivors who didn’t get infected—independent of delays in care.
Case series from cancer patients with liver metastases infected by Covid‑19 reported extremely high serum IL‑6 levels (over 16–21 pg/mL).
These patients deteriorated rapidly and died within days—even when metastases were previously stable.
Other broader studies show that while acute fever linked to infection can sometimes improve outcomes in breast cancer, the underlying IL‑6 rs1800796 genetic variant influences the effect.
For example, women with the CC genotype—when experiencing a fever—showed better progression-free survival.
However, elevated inflammatory markers like IL‑6 and CRP (C‑reactive protein) are repeatedly associated with worse survival, especially in metastatic breast cancer cases.
A specific IL‑6 promoter SNP, rs1800795 (GG genotype), correlated with increased odds (OR ~1.5–2.2) of developing distant metastasis.
Why It Matters: Mechanistic Insights and Clinical Significance
IL‑6 is well-known to promote tumor growth, invasiveness, and immune suppression through the JAK/STAT3 pathway.
It also supports epithelial‑to‑mesenchymal transition (EMT)—a key process in metastasis.
These findings highlight IL‑6 not just as a biomarker, but a therapeutic target. Early-phase clinical trials are already exploring IL‑6 or IL‑6 receptor blockday
—e.g., combining trastuzumab with the anti‑IL‑6R antibody tocilizumab in metastatic HER2-positive breast cancer.
Importantly, in individuals who underwent chemotherapy or radiation, immune defenses remain weakened for months.
This makes them particularly vulnerable to severe infection—and potentially to the reawakening of dormant cancer cells.
What Cancer Survivors Should Know
Risk Factor Impact
Respiratory viral infection (flu or Covid‑19) May trigger inflammation leading to metastatic relapse by activating lung-resident dormant breast cancer cells.
High IL‑6 serum levels Associated with poorer prognosis and rapid progression in metastatic breast cancer.
Certain IL‑6 genetic variants (e.g. rs1800795 GG) Linked to increased risk of metastasis.
The research suggests that for cancer survivors—particularly in the critical first year of remission—respiratory infections may carry elevated risk.
Bottom Line & Practical Advice
This evolving body of evidence underscores a critical take-home point: common respiratory viruses like Covid‑19 and influenza
may pose risks beyond the acute illness—they may trigger cancer relapse in susceptible individuals.
If you’ve survived breast cancer:
Stay up-to-date with flu and Covid vaccinations.
Use precautions (like masking and hygiene) during outbreaks.
Monitor symptoms carefully, and report respiratory infections promptly to your medical team.
Discuss with your oncologist whether monitoring of IL‑6 levels or inflammatory markers could inform personalized risk assessments.
Ask about emerging anti‑IL‑6 therapies or clinical trials, particularly if you’re at higher risk due to tumor biology or genetics.
Animal models showed a 100-fold surge in lung tumor cells within days of respiratory virus infection.
Human data confirm increased risk of metastasis and death following respiratory infections in cancer survivors.
IL‑6 stands out as a mechanistic mediator—and a promising target for future therapies.
Stay informed, stay proactive—and don’t hesitate to reach out to your healthcare provider about your individual situation.
This new research could redefine protective strategies for cancer survivors.
FAQs
Covid, Flu, and Breast Cancer Risk
1. Can Covid-19 really reactivate breast cancer?
Yes. New research suggests that Covid-19 may reactivate dormant breast cancer cells, especially in the lungs, increasing the risk of metastasis.
2. How do viruses like flu or Covid cause this?
They trigger a strong inflammatory response in the body. This inflammation—especially via the cytokine IL-6—can wake up dormant cancer cells and make them start growing again.
3. What are dormant breast cancer cells?
These are cancer cells that have spread from the original tumor to other organs (like the lungs) and remain inactive for years before suddenly reactivating.
4. Is this proven in humans or just in animals?
Both. The study used mouse models and human cancer patient data, showing consistent patterns of increased metastasis after respiratory infections.
5. Are survivors of other cancers also at risk?
While the study focused on breast cancer, other cancers with dormant cell behavior (like prostate or colon) may also be affected. More research is ongoing.
6. What is IL-6, and why is it important?
IL-6 is a protein (cytokine) released during infections. It promotes inflammation and was found to be a key driver in reactivating dormant cancer cells in the study.
7. What symptoms should cancer survivors watch for after an infection?
Persistent cough, chest pain, unexplained fatigue, or shortness of breath could be red flags. Always consult a doctor if symptoms worsen after recovery from flu or Covid.
8. Does vaccination help reduce this risk?
Yes. Staying up to date with Covid-19 and flu vaccines can reduce the severity of infections, lowering the inflammatory response that might trigger cancer reactivation.
9. How soon after infection can cancer cells reactivate?
In mice, metastatic growth began within days. In humans, the risk of relapse seems highest within the first year after infection.
10. Can IL-6 be tested in cancer patients?
Yes. Blood tests can measure IL-6 levels. It may help in assessing risk, though it’s not yet a standard screening tool in cancer care.
11. Are there treatments targeting IL-6?
Yes. Drugs like tocilizumab (used in severe Covid cases) block IL-6 and are being explored in cancer trials for their potential to prevent metastasis.
12. Should breast cancer survivors be extra cautious during flu season?
Absolutely. Preventive measures like flu shots, wearing masks, and avoiding crowded places are recommended for high-risk individuals.
13. Can stress or non-viral inflammation also trigger dormant cancer cells?
Yes. Chronic inflammation from stress, autoimmune disease, or other infections may contribute—but respiratory viruses seem to have a more direct effect.
14. Is this a concern only for recent cancer survivors?
The first year after remission is the most critical, but the risk may persist for years, especially in those with known dormant cell spread.
Your IL-6 levels or inflammation status
Vaccination updates
Any preventive strategies during infection waves
Eligibility for clinical trials involving IL-6 blockers
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