Your immune system normally defends your body against harmful substances to prevent infection and illness. When your immune system malfunctions, harmful substances like cancer cells may be able to escape detection and elimination.

In multiple sclerosis (MS), a person's immune system malfunctions and attacks nerve fibers and their protective myelin covering in the brain and spinal cord. Due to this abnormal immune system response, it's reasonable to think that MS may be associated with increased cancer risk.

While some research studies have found a link between MS and cancer risk, others have found no such connection. Some studies have even found a reduced risk of cancer in people with MS.

This article will briefly examine the possible link between MS and cancer risk and why study results may be conflicting. In addition, strategies to help prevent cancer when living with MS will also be explored.

Research on MS and Cancer

The scientific evidence examining whether having MS increases your risk for cancer remains inconclusive.

Here are a few examples of studies that have examined the MS/cancer connection:

• In one study, researchers investigated cancer rates among French people with MS compared to the general population. People with MS were found to have an increased cancer risk, especially for prostate cancer, colorectal (colon and rectum) and anal cancer, and trachea/bronchus/lung cancer.
  
• Using information from a United Kingdom database, researchers found that the cancer risk of those living with MS was similar to a control population (people without MS). However, the number of cancer diagnoses increased over time among the people living with MS. This was not seen in the control population.
• In another study, using data from Canadian cancer registries and health records of people with and without MS, researchers found a possible increased rate of bladder cancer in people with MS compared to those without MS. No increased rates of breast cancer or colorectal cancer were found.
• In a Norwegian study, researchers examined the rate of new cancer cases among people with MS and the general population. During the years 1953–1995, people with MS did not have a higher cancer rate; however, during the years 1996–2017, people with MS had increased rates of cancer of the brain, urinary tract organs such as the bladder, and respiratory organs, including the lungs.
  
• In a large systematic review (a study of all existing literature on the topic), researchers pooled together data from multiple studies that had assessed cancer risk in people with MS. They found a lower risk of cancer in people with MS compared to the general population.

Risk Factors

It's unclear why results from studies examining the association between MS and cancer risk are conflicting. Different study methods and patient populations may somewhat explain the mixed findings. Lifestyle factors, MS symptom-related factors, and the medications used to treat MS also probably play a role.

Lifestyle Factors

According to the American Cancer Society, nearly 20% of all cancers diagnosed in the United States are linked to various lifestyle factors, including obesity, physical inactivity, excess alcohol consumption, and/or poor nutrition.

Differences in lifestyle factors among people living with MS and those not affected by MS would likely impact cancer risk. These differences may not have been teased out in various studies.

For example, in the study that found a possible increased rate of bladder cancer in people with MS, researchers noted that they could not account for differences in smoking, diet, and physical activity.

This is important since smokers have a higher chance of developing MS, and excessive smoking is linked to an increased risk of bladder cancer and trachea/bronchus/lung cancer.

Along the same line, it's known that obesity in early adulthood may contribute to an increased risk of developing MS. Obesity is also associated with a higher risk of colorectal cancer.

MS Symptom-Related Factors

MS symptom-related factors can also affect cancer risk.

For instance, people with MS may be at an increased risk for bladder cancer not because of MS-related inflammation but because they are more likely to experience urinary tract infections and use chronic indwelling catheters (those left in the body to promote urine drainage) compared to the general population.

It's also possible that compared to the general population, people with MS are either more likely or less likely to undergo cancer screenings and be diagnosed with cancer. They may have better access to cancer screening tools through their MS provider. Alternatively, maybe their MS care competes with their time for preventive cancer screening tests.

MS Treatments

Taking an MS disease-modifying therapy (DMT) could certainly influence a person's cancer risk, as most MS DMTs work by suppressing or altering the immune system.

This influencing factor is supported by the Norwegian study that found that cancer rates in people living with MS increased with the introduction of DMTs.

Prevention

If you or a loved one has MS, it's reasonable to gain knowledge about how cancer may be associated with MS. Nevertheless, it's important to not get too worried by all the research study nuances.

Instead, focus on the big picture. There is no evidence that MS causes cancer—rather, MS may alter your chances of developing cancer or certain types of cancer.

While this statement can still feel overwhelming, the good news is that there are healthy lifestyle habits you can adopt to help lower your cancer risk.

These healthy habits include:

• Avoiding smoking and excess alcohol consumption
• Maintaining a healthy body weight
• Engaging in regular physical activity
• Eating a nutritious diet that is rich in fruits, vegetables, and whole grains and low in saturated fats (e.g., red meats or highly processed foods)

The above habits have the added bonus of potentially improving your outlook while living with MS. They can also help prevent other serious conditions like heart disease and diabetes.

In addition to achieving a healthy lifestyle, be sure to carve out time in your schedule for undergoing appropriate cancer screenings—for example, a mammogram to screen for breast cancer or a colonoscopy or stool test to screen for colorectal cancer.

Summary

The research examining whether having MS affects your risk for developing cancer is mixed. While some studies have found a boost in cancer risk among people with MS, others have not. Conflicting study results can probably be explained at least partially by lifestyle factors and the emergence of MS disease-modifying therapies.

Understanding how MS may affect your risk for cancer is important as it may change how and when you begin certain cancer screening protocols. In the meantime, adopting healthy lifestyle behaviors like engaging in regular exercise and eating a well-balanced diet can help prevent cancer.

A Word From Verywell

Coping with a lifelong disease like MS is no easy feat. It requires inner strength, support from loved ones, and a trusting relationship with your healthcare team.

As you continue to gain knowledge about MS, remain focused on what you can control in life. This includes taking your MS medication, attending your healthcare appointments, upholding a positive mindset, and eating a well-balanced diet.