a doctor studying myasthenia gravis and cancer risk

How Do Autoimmune Diseases Affect Cancer Risk?

Our immune system is constantly working to fight foreign or dangerous invaders like viruses, fungi, or bacteria. This helps protect us from things like infections, the flu, and even cancer cells.1

However, in some people, the immune system cannot tell the difference between healthy cells and harmful invaders. Because it cannot tell the difference, the body begins to attack and damage healthy cells. This results in autoimmune disease, which often causes inflammation in the body. Research has long shown that inflammation may increase cancer risk.1

What has previous research found?

Earlier studies have found that several autoimmune diseases increase cancer risk in their related body parts. For example, people with celiac disease have a higher risk of small intestine cancer.2,3

However, a 2020 study found that there is also a link between autoimmune disease and cancer in distant organs. In that study, people with rheumatoid arthritis (RA) showed a higher risk of lung cancer or lymphoma.3

Despite these effects, there has been little research on the link between organ-specific autoimmune diseases and the risk of cancer in the involved organs, near and distant organs, and different systems. In the first study its kind, experts looked at this possible connection. The results were published in late 2021 in the Journal of American Medical Association (JAMA).2

What did the JAMA study examine?

To better understand the possible link, researchers looked at the medical records of nearly 500,000 adults who agreed to be part of the study. They ranged in age from 37 to 73 years old.2

The researchers looked at the records for 48 autoimmune diseases, including:2

They also looked for a range of cancer types, including:2

  • Ovarian cancer
  • Breast cancer
  • Bladder cancer
  • Leukemia
  • Lung cancer
  • Melanoma
  • Prostate cancer

What did the study find?

Many autoimmune diseases the researchers studied did not show a higher risk for a specific kind of cancer. However, they found some that did.

Specifically, ulcerative colitis and asthma were linked to a higher overall risk of cancer. Also, people with any autoimmune disease had a higher risk of developing certain cancers. These included lung cancer, lymphoma, and liver cancer.2

Researchers also found that 5 organ-specific autoimmune diseases were significantly linked to a higher risk of cancer in those organs, such as asthma with lower airway cancer.2

Nine autoimmune diseases were linked to an increased risk of cancers in the nearby organs. This includes asthma with lung cancer and celiac disease with small intestine cancer.1

The study also found that 13 autoimmune diseases were linked to an increased risk of cancer in the nearby organs, distant organs, or different systems. Examples include:2

  • Crohn's disease with liver cancer
  • Autoimmune hepatitis with tongue cancer
  • Ulcerative cancer with prostate, colorectal, liver, and tongue cancers

Notably, RA had a 2-way effect in the study. People with RA had a higher risk of lung cancer and lymphoma. But they also showed a lower risk of prostate cancer and breast cancer.2

What does this mean?

The results of the study do not mean that a person with a specific autoimmune disease is going to get cancer. However, it is important to keep cancer risk in mind if you have 1 or more autoimmune diseases. While there are no surefire ways to prevent cancer, you can reduce your risk by:2,4

  • Not using tobacco
  • Eating healthy
  • Staying active
  • Using sun protection
  • Getting vaccinated, especially against hepatitis B and human papillomavirus (HPV)
  • Practicing safe sex, like using condoms or dental dams and getting regularly tested for sexually transmitted infections
  • Not sharing needles
  • Getting regular medical care, including self-exams and regular cancer screenings

The study findings may help drive more research to better understand the link between autoimmune diseases and cancer.

If you live with an autoimmune disease, talk to your doctor about the best ways to manage your condition and reduce your cancer risks.

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