When your immune system is functioning normally, it protects your body against damage, including cancer. When your immune system isn’t working properly, cancer cells can go undetected and grow into tumors. Because malfunctions in the immune system lead to multiple sclerosis (MS), it’s understandable to wonder whether cancer and MS could be linked. Certain disease-modifying therapies (DMTs) used to fight MS can also raise the risk for developing cancer.

Read on to learn more about the relationship between MS and the risk of cancer, as well as what to ask your doctor if you have concerns about your own risk.

How Does Having MS Affect Cancer Risk?

Research on whether MS increases or decreases your risk of getting cancer has mixed results. Some studies have linked MS to a higher chance for some types of cancer, and others concluded that having MS may provide protection from cancer.

Increased Cancer Risk

Certain studies have found MS leads to an increased rate of cancer, but the research shows conflicting results. Here are brief summaries of the most significant studies indicating a higher risk of cancer in people with MS:

• A study in France found the risk of cancer was higher for people with MS, specifically for prostate, colorectal, anal, breast, tracheal, bronchial, and lung cancers.
• A study in Taiwan found people with MS had a higher risk of cancer overall, and breast cancer in particular.
• A study in Canada found no increased risk of breast and colorectal cancer, but an increased risk of bladder cancer.
• A study in Italy found a higher risk of cancer in people with MS, but only for those who had previously taken immunosuppressant medications.

More studies have been published, but the ones listed above represent a good summary.

Decreased Risk of Cancer

A number of research studies suggest that having MS has a protective effect against getting some types of cancer. In other words, these research results imply that if you have MS, your risk of certain cancers seems to be lower as compared to the general population.

• One study in British Columbia and another international study found overall cancer risk was lower for those with MS.
• A study in France found that about 7 percent of participants with MS reported ever having cancer, compared to about 12 percent of the people in the study who didn’t have MS. Use of immunosuppressant medications did not seem to impact this risk.

The Bottom Line

For now, the answer to the question of whether MS increases or decreases cancer risk is inconclusive, but it’s an area of active interest in the field of neurology. While no clear conclusion can be made about the risk of cancer and MS, it’s possible that having MS makes some cancers harder to treat. A recently published Norwegian study following individuals over 65 years concluded that people with MS have a higher risk of death after a cancer diagnosis.

Possible Links Between Cancer and MS

There are many theories about why MS and cancer risk might be connected. These include the effects of an overactive immune system, a person’s genetic makeup, and exposure to environmental factors or the Epstein-Barr virus (EBV).

Inflammation

One of the leading theories about the relationship between MS and cancer is the involvement of the immune system in both conditions. Some researchers think the immune system overactivation that causes MS also causes your immune system to ramp up its monitoring for problems in the body. This higher degree of immune surveillance, as scientists call it, might result in the body detecting and fighting cancer sooner.

On the other hand, the long-standing inflammation from MS could also damage tissues, leading to a higher risk of cancer. Additionally, inflammation of the central nervous system (or CNS, which includes the brain and spinal cord) in MS is a risk factor for nervous system cancers.

Epstein-Barr Virus

Epstein-Barr virus infection is known to be involved in the development of some cases of MS, as well as other autoimmune diseases. EBV has also been linked to certain types of cancers, including Hodgkin lymphoma, Burkitt lymphoma, and cancers of the nose and throat. More research is needed to determine the cancer risk in people who have EBV-related MS.

Genetics

Some studies show an increased risk of breast cancer for people with MS. Certain types of breast cancer have known genetic risk factors, such as the BRCA1 gene mutation. A case study of one family with histories of both MS and breast cancer theorized a genetic mutation may have raised the risk for developing both conditions.

Environmental Risk Factors

Many risk factors for cancer are also risk factors for developing MS. Multiple risk factors together are responsible for ultimately developing cancer, and we often don’t know exactly how or why. The same is true for MS. Some examples of known risk factors for both cancer and MS include:

• Viral infections
• Higher body weight
• A history of tobacco use
• Air pollution

Reducing the risk of cancer is important for anyone, but especially if you’re already living with MS. Quitting smoking, maintaining an active lifestyle, and eating a healthy diet are all things you can do to feel your best and reduce your risk of cancer.

Disease-Modifying Therapies

DMTs have proven effective in preventing MS relapses and slowing the progression of the disease. DMTs work by immunosuppression –– meaning they impair aspects of your immune system that attack the nervous system. However, your immune system –– while overactive in MS –– also protects you from cancer and infection.

Taking a DMT is a balance between risks and benefits for your condition. You and your neurologist can discuss the risks, side effects, and benefits of your treatment options.

Which DMTs May Raise the Risk for Cancer?

Some DMTs have been shown to increase the risk of certain types of cancer because they reduce the body’s ability to fight cancer cells. A 2021 international review of nearly 6,000 cancer diagnoses for people with MS who were also treated with DMTs found certain drugs may increase cancer risk. These included:

• Dimethyl fumarate (Tecfidera)
• Fingolimod (Gilenya)
• Interferon beta
• Natalizumab (Tysabri)

The same study found use of the following medications did not seem to increase cancer risk:

• Alemtuzumab (Lemtrada)
• Glatiramer acetate (Copaxone)
• Ocrelizumab (Ocrevus)
• Teriflunomide (Aubagio)

Some other DMTs have isolated reports of just a few cases of cancer that may or may not be linked. However, your cancer risk is also related to a family history of cancer, environmental risk factors, and how long you take certain DMTs and at what dose.

Some DMTs Are Used To Fight Cancer

Some medications that are used as DMTs for MS, such as cladribine (Mavenclad) and rituximab (Rituxan), are currently used for cancer treatment. Others (dimethyl fumarate, fingolimod, and teriflunomide) are currently being studied as potential cancer treatments.

MS is a progressive disease, meaning disability can accumulate over time. When considering cancer risk, it’s important to remember DMTs are the only treatments proven to slow MS. Treatment decisions are best made as a close collaboration between you and your neurologist. They’re the best person to help you weigh your potential benefits and risks when taking a DMT.

Talk With Others Who Understand

MyMSTeam is the social network for people with MS and their loved ones. On MyMSTeam, more than 198,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you living with MS and concerned about your risk of cancer? Have you talked with your health care team about ways to lower your risk? Share your experience in the comments below, or start a conversation by posting on your Activities page.