Does COVID-19 Cause Cancer, or Could It Protect Against Cancer?

During the COVID-19 pandemic, the health problems caused by the virus also raised questions about its long-term effects. One issue is whether COVID-19 is related to cancer. Different studies have suggested that the virus might trigger cancer development or, in some circumstances, protect against cancer. This article examines the relationship between COVID-19 and cancer in detail in light of recent scientific studies.

What Are the Possible Links Between COVID-19 and Cancer?

A study conducted in 2023 suggested that COVID-19 might be associated with several types of cancer.

Analyses using genetic data indicate that people genetically predisposed to severe COVID-19 have an increased risk of the following cancers:

• Stomach Cancer: 24% higher risk

• HER2-Positive Breast Cancer: 9% higher risk

• Esophageal Cancer: Minimally increased risk

• Colorectal Cancer: Minimally increased risk

• Colon Cancer: Minimally increased risk

Another study, from 2024, showed that COVID-19 infection and hospitalization might increase the risk of developing multiple myeloma and that immune-function-related genes such as LZTFL1, MUC4, and OAS1 were involved in this association.

A case series published in Brazil in 2022 described three young adults who, 2-3 months after COVID-19 infection, received a hematological cancer diagnosis. These cases support the hypothesis that COVID-19 might activate latent, or dormant, cancers.

Severe COVID-19 May Signal an Undiagnosed Cancer

A large study published in 2023 found that patients treated in intensive care for severe COVID-19 had a 31% higher risk of receiving a cancer diagnosis after hospitalization. Diagnoses of kidney, hematological, colon, and lung cancers increased particularly noticeably. This raised the possibility that severe COVID-19 could be a sign of an undiagnosed cancer.

Could COVID-19 Increase Cancer Metastasis?

A study presented at a special meeting of the American Association for Cancer Research in 2024 suggested that COVID-19 increased the risk of lung metastasis and cancer-related death in patients with cancer. Experiments in mice showed that COVID-19 infection accelerated the spread of breast cancer cells in the lungs.

How Could COVID-19 Cause Cancer?

Possible mechanisms by which COVID-19 might increase cancer risk include:

• Cytokine storms and chronic inflammation: These may increase genomic instability and trigger tumor formation.

• Dysregulation of the renin-angiotensin-aldosterone system: This may be triggered by viral infection and lead to cancer.

• Viral mutagenicity: Genetic changes caused by the virus in cells may promote tumor formation.

• Activation of latent cancer cells: This may lead to the release of factors that increase lung metastasis, particularly in breast cancer.

How Viruses Can Trigger Cancer

Figure explanation: Certain viruses, such as HPV, hepatitis B and C viruses, and EBV, can infect human cells, establish long-lasting infections, and eventually lead to cancerous changes. These viruses evade the immune system and persist in the body. If a virus can multiply and spread, it can infect new hosts.

After entering a human cell, a virus may integrate its genetic material into the cell's DNA and begin replicating. Certain proteins called viral oncoproteins are produced during this process. They suppress mechanisms of cell death and trigger uncontrolled cell proliferation.

These events cause abnormal cellular changes. Cell death decreases while cell proliferation increases. Uncontrolled cell division leads to the accumulation of DNA errors and genomic instability. Viruses that evade the immune system cause chronic inflammation. Inflammation and external factors, such as accompanying carcinogens including tobacco and alcohol, further increase genomic instability. Reactive oxygen species (ROS) produced by chronic inflammation increase DNA damage and accelerate cellular changes.

Together, these factors may transform a normal cell into a cancer cell. This process can be triggered by known oncoviruses such as HPV, associated with cervical cancer, and hepatitis B and C viruses, associated with liver cancer. Researchers are now investigating whether SARS-CoV-2 might have a similar effect in certain cancers. 

Could COVID-19 Protect Against Cancer?

Interestingly, some research also suggests that COVID-19 might have a protective role against certain cancers. For example, people predisposed to severe COVID-19 have been observed to have a significantly lower risk of laryngeal cancer.

Another study conducted in 2024 found that the inflammatory state during COVID-19 might enhance the immune response against metastatic tumors and cause some cancers to regress.

Cases of Spontaneous Cancer Regression After COVID-19

A review published in 2023 reported 14 tumor cases that regressed spontaneously after SARS-CoV-2 infection and, after COVID-19 vaccination, 2 cases of regression, or tumor shrinkage. These findings suggest that COVID-19 might activate the immune system and trigger an immune response against cancer cells.

Conclusion: More Research Is Needed

Current findings on the relationship between COVID-19 and cancer remain inconclusive. Given that oncogenesis takes a long time, there is not yet robust evidence that SARS-CoV-2 directly causes cancer. However, the indirect effects of the pandemic on cancer diagnosis and treatment must also be considered. Future comprehensive research will help clarify this relationship.

We will continue to follow scientific developments on this topic.