Dear Dr. Roach: Are cancers and COVID considered to be autoimmune diseases? Someone said this to me recently, but I have never heard this before.
No, both cancers and COVID-19 infections are essentially failures of the immune system. The job of the immune system is to keep us safe from invaders — either outside invaders like bacteria, viruses, fungi and parasites, or inside invaders like cancer — when the body’s own cells start growing uncontrollably.
The immune system is amazingly good at its job, but unfortunately, the pathogens we encounter are also very good at escaping the immune system. Cancers also have many ways of bypassing the immune system’s control. An autoimmune disease, such as Type 1 diabetes, multiple sclerosis and lupus, occurs when the immune system mistakenly recognizes part of the body as an invader. The immune system then attacks and damages the body.
The targets for Type 1 diabetes are the beta cells of the pancreas, with the result being that a person is unable to make insulin. Joints, the kidney and the skin are all targets for lupus; whereas for multiple sclerosis, it’s the cells making myelin in the central nervous system that are the targets of attack. I’m simplifying things because the issues are complex. What triggers the autoimmune response isn’t always known.
Vaccines give the immune system help ahead of time and can prevent many infections and a few cancers. There is much active research being done now to make better vaccines to both treat and prevent other cancers.
Dear Dr. Roach: I am 70. Due to breast cancer history in my family and a diagnosis of atypical ductal hyperplasia in a lump that was removed, I get MRIs with and without imaging agents annually.
Do I have to be concerned about gadolinium being retained in my body? With annual MRIs, how long does it take to build up in the brain, bones and organs? Would it make sense to get the MRI without an imaging agent every other year? How do I decide the risk versus the benefit?
The MRI contrast material is based on gadolinium. Although some people can have retention of gadolinium in the brain, it is not clear that this leads to any clinical symptoms. Similarly, gadolinium can be found in the skin, bone and liver, but it’s not clear whether these lead to problems. After decades of using these agents, the risk of clinical disease seems to be very low.
The bigger issue is the kidney. Some gadolinium agents, which are no longer used in the U.S. or Europe, are associated with a condition called nephrogenic systemic fibrosis. It is only found in people with advanced kidney disease, and it may also be associated with older gadolinium contrast agents. The risk of gadolinium-induced kidney disease is minimal with newer agents and in people without pre-existing kidney disease.
In my opinion, for people without kidney disease, gadolinium toxicity is not a significant risk, and you should get the recommended screening test ordered by your specialist. In people with mild chronic kidney disease (called CKD stage 2 or 3), gadolinium is probably safe, but in people with stage 4 CKD, it should probably be reconsidered. There are times when an MRI is so important that it is worth the risk, in which case we use the agents with the best safety record, but the oncologist still needs to consider other ways of screening.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu