What is the connection between autoimmune diseases and cancer?

Many of us have heard that our autoimmune diseases put us at an increased risk for cancer, but what is the connection between cancer and autoimmune diseases? The two are similar in that they can both involve dysfunctions of the immune system. Cancer often develops when our immune system fails to attack defective cells. On the other hand, autoimmune diseases develop when our immune system is overactive and attacks our cells.

Firstly, autoimmune diseases can lead to chronic inflammation, which is a risk factor for cancer. Patients with autoimmune diseases that attack specific organs will be at an increased risk of developing cancer in those organs. For example, patients with Crohn's disease, Celiac disease, or ulcerative colitis are at an increased risk for colorectal cancer, and patients with pernicious anemia or autoimmune gastritis are at higher risks of developing gastric cancer. Below are a few known associations of common autoimmune diseases in our registry and cancer risks:

Secondly, certain medications taken by patients with autoimmune diseases may put the patients at an increased risk for cancer. In particular, immunosuppressants turn off a part of the body's immune system, and thereby reduce the body's ability to destroy cancerous cells.

Finally, certain cancers and cancer treatments can cause autoimmune diseases. When the immune system attempts to fight off the cancer cells, it can become too active and develop autoimmunity. For example, patients with leukemias and lymphomas can develop warm autoimmune hemolytic anemia. Certain cancer treatments like immunotherapy, which activates the immune system to attack cancer cells, can also cause autoimmune diseases as a side effect.

All of these risks were identified through studies of subsets of the patient population. What other connections can we find when we have more data on autoimmune disease patients? This is why it's so important to have a centralized autoimmune disease registry. Like the National Cancer Registry, ARI wants to be able to forecast autoimmune disease patients' likely outcomes. Please help us achieve this by joining our registry and sharing our information on social media. Donations are also greatly appreciated!

Sources:
Hashimoto's: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9318815/
Rheumatoid arthritis: https://www.rheumatologyadvisor.com/home/topics/rheumatoid-arthritis/rheumatologists-cancer-risk-management-patients-with-rheumatoid-arthritis/
Lupus: https://www.hopkinslupus.org/lupus-info/lifestyle-additional-information/lupus-cancer/
Sjogren's: https://sjogrenssyndromenews.com/news/analysis-finds-increased-risk-cancer-sjogrens-syndrome-patients/
Mixed connective tissue disease: https://www.hmpgloballearningnetwork.com/site/autoimmune/web-content/connective-tissue-diseases-associated-increased-risk-nonmelanoma-skin-cancer