Are Certain Types of Cancer Related to NMO?
In many cases, neuromyelitis optica spectrum disorder (NMOSD or NMO) occurs alongside other health issues. For example, someone with NMO may also have another autoimmune condition. This is a condition where the immune system mistakenly attacks itself.1
NMO and cancer
Research shows that people with NMO may also have cancer. Although the exact number is unknown, anywhere from about 1 percent to 12 percent of people with NMO may go on to be diagnosed with cancer.1,2
When a person has cancer, many processes in their body are affected. Specifically, the immune system may not function normally. The immune system may create more inflammation that can cause damage throughout the body, regardless of where the specific cancer is. The body may also produce antibodies in its attempt to fight cancer.1-3
Antibodies are proteins that help fight germs and other invaders. Just like in NMO, these antibodies can mistakenly attack healthy parts of the body and cause issues. Other health issues caused by a cancer somewhere in the body are called paraneoplastic disorders. Neoplasm or neoplastic process are other terms for cancer.1-3
Is NMO a side effect of cancer?
In some paraneoplastic disorders, the body makes antibodies that attack the spinal cord and optic nerve, which controls vision. This can cause NMO-like symptoms, including optic neuritis and transverse myelitis. This is inflammation of the optic nerves and spinal cord.1,3
This can make it hard to determine if a person’s symptoms are due to NMO or the effects of an underlying cancer. This is why some experts suggest screening for underlying cancer when a person who is unlikely to have NMO, such as older adults, has NMO-like symptoms.1
Why might symptoms overlap?
Doctors have many ideas about why the body's response to cancer could cause NMO-like symptoms. As mentioned, it could be that the body makes antibodies similar to those in NMO. However, it could also be that the body makes the exact same antibodies in both situations. Specifically, the AQP4-IgG (aquaporin-4) antibody may be present in both NMO and cancer.1,2
AQP4 is important in helping the cells in our body maintain their water balance. Some experts have found that certain cancer cells make more AQP4 to help them grow. In response, the body may try to make AQP4 antibodies (AQP4-IgG) to attack these cancer cells and stop their spread.1,2
These antibodies may lead to NMO symptoms, just like they do in people with NMO who do not have cancer. However, it is possible to have both cancer and AQP4 antibodies without NMO symptoms. This suggests that there are also other factors at play.2
NMO and cancer overlap
One review studied many different cases of NMO and cancer occurring together. The experts leading the review found that about 80 percent of all tumors in the cases studied tested positive for the AQP4 protein. In addition, around 95 percent of cases tested positive for AQP4 antibodies (AQP4-IgG).1
The cases studied were also split evenly:1
- About 1 in 3 were diagnosed with NMO before cancer
- About 1 in 3 were diagnosed with NMO after cancer
- About 1 in 3 were diagnosed with NMO and cancer around the same time
In some cases, treating the underlying cancer also improved NMO symptoms.1
While many different cancers were reported in the cases studied, some types were more common than others. The most common types of cancer diagnosed in people with NMO were:1
- Cancers of the genital or urinary tracts (genitourinary) – 22 percent
- Breast – 19 percent
- Lung – 19 percent
- Gastrointestinal – 11 percent
- Blood cancer – 10 percent
Specific genitourinary cancers identified were ovarian cancer in women and prostate cancer in men.1
Is there a link between NMO and cancer?
Determining whether or not NMO and cancer are directly linked is tricky. As mentioned, NMO-like symptoms may be a side effect of cancer somewhere in the body. However, it may be that people with both NMO and cancer developed each separately. This is especially true for older people who are already at a higher risk of having cancer.1,2
It may also be possible that some treatments for NMO increase the risk for cancer. For example, drugs that impact the immune system, such as cyclophosphamide, may help NMO but also increase the risk of urinary tract cancers.1
Much more research is needed to determine the true relationship, if any, between NMO and cancer. However, some experts argue for increased cancer screening in people with NMO or those who develop NMO later in life.1,2
If you are concerned about your risk for cancer, talk with your doctor. They can recommend specific screening options for your situation.
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