Does MS Increase Cancer Risk?

Content Producer

A study published early in 2014 found that people with multiple sclerosis (MS) may have an increased risk of developing cancer, particularly breast cancer. But other studies, conducted less than two years ago, concluded that MS patients have lower risk of cancer. These conflicting findings may have people with MS wondering what their risk really is, and more importantly, how to reduce any potential risk. In order to help gain better understanding of the possible link between cancer and MS, we discussed the topic with Kathleen Costello, Associate Vice President of Clinical Care at the National Multiple Sclerosis Society (NMSS).

What are most studies focusing on specifically when it comes to MS and cancer risk?

The studies on MS and cancer risk that I have recently reviewed have been retrospective studies that looked at a particular population of people with MS and compared their incidence of cancer to a similar group that did not have MS to determine whether there was any increased or decreased risk of cancer in the MS group. The results of the studies since the mid-1990s have been quite variable and have indicated no increased risk, some increased risk or decreased risk of cancer in the people with MS. One meta-analysis conducted in 2010 that involved more than 45,000 people actually found a decreased risk of cancer in people with MS. I think that people with MS want a more definitive answer, but I don’t believe—given the results so far—that there’s been a definitive answer regarding whether MS increases, decreases or has no effect on cancer risk.

So why do some reports say that there is a link between MS and cancer risk?

In a particular population of people studied there may have been an indication of an increased risk. It is important to look at the study populations and whether other cancer risk factors were considered as they may have influenced the findings. It is also important to consider the other studies that have been done and their results.

Going forward, what type of studies can help scientists better understand the link?

Ideally,  a prospective study where subjects are followed moving forward over time and where known risk factors for cancer are accounted for would be very useful, but would also be a long term study. The studies that have been done thus far are retrospective or looking back over time. In these studies, the contribution of other risk factors was not always known.  So if a retrospective study is done, ideally, the additional risk factors for cancer would need to be accounted for to determine if MS could be singled out as an independent risk factor.

What are some examples of the variables that studies are focusing on?

Many of the previous studies that have been done investigating possible cancer risk in MS looked retrospectively at overall cancer occurrence over time.  Many also looked at the specific types of cancer that occurred and if the number of people who had MS and cancer were higher or lower than people who developed cancer who did not have MS. The results of these studies are variable, and while a few suggest an increased risk of cancer in the MS groups, several also indicate a decreased risk of cancer in the MS groups. In the recent study that looked at a cancer risk in a MS population in Taiwan, the study results suggest an increased risk of cancer, particularly breast cancer, in the MS group. However, the authors point out limitations in the study including a lack of information about lifestyle factors that may have influenced the results. In addition, they note other previous studies in large populations that do not indicate an increased risk of cancer in the MS patients studied.

Is there evidence of a link between MS and other conditions?

There are some other diagnoses that occur more frequently in people with MS. People with MS have more mood disorders than the non-MS population. In addition there are more sleep disorders. Since MS is an immune-mediated disease, people with the condition may have more likelihood of having another auto-immune disease.

Is it important for people with MS to discuss risk of cancer with their doctors?

I don’t know if it’s necessarily a top question for their MS doctor, but perhaps it is a discussion to have with their primary care provider. There are a lot of modifiable risk factors for cancer, and I think they should be discussed. Perhaps with more discussion about risk factors, the more attentive and proactive people can be in modifying those risk factors. Examples of modifiable risk factors  include smoking, lack of exercise, obesity, excessive alcohol consumption, sun exposure and certain medications, such as hormones that are used in postmenopausal women that may increase risk for breast cancer.

What happens if someone has both MS and cancer?

If someone would happen to have both at the same time, cancer treatment is going to trump the treatment for MS because the cancer is potentially fatal. And that is a question that some people with MS do have. For instance, “I’ve been diagnosed with a type of cancer. Now what I do about my MS?” Or, “If I’m on a particular drug for MS, and I am diagnosed with cancer, how does that influence the drug that I’m on?” Generally speaking, your treatment for your cancer is going to be the most important due to the potential for a fatal outcome. Some of the treatments for MS may not be appropriate to use with a cancer drug.  Some of the treatments for cancer can actually be useful or beneficial for the MS. When treating cancer, often some type of immuno-suppressant chemotherapy is used. And that may have a beneficial effect on MS because it can also suppress the activity of the immune system that can be provoking MS activity. It is very important when there is a diagnosis of cancer requiring drug treatment in someone on treatment for their MS that the healthcare providers for each discuss the treatment plan.

Why is this research important, and why should people with MS take notice?

I think people stand up and take notice when cancer is mentioned because cancer can be fatal and we obviously care a lot about that. We also care a lot about the things that can be done to reduce cancer risk.. So if there is a known increased risk it would allow us to be more proactive in our surveillance and assessments so that if cancer is diagnosed, perhaps it would be diagnosed early and treatment could be initiated as soon as possible.

What should be the biggest takeaway for people with MS?

I think in terms of a risk association, the studies so far have not been able to definitively conclude that there is an increased risk of cancer in those people who have MS.  I don’t believe that given all of the studies that have been done, that there is conclusive evidence of increased risk of cancer due to MS. I think that the results remain conflicting, and additional well-designed studies need to be done to determine if there really is an association between MS and risk of cancer.

Having said that, cancer is a serious diagnosis, so I think that maybe the most important thing is to look at what we do know about risk of cancer and to carefully look at those modifiable risk factors and modify them when possible. Smoking is a huge risk factor for many different types of cancers. It’s also a risk factor in worsening MS, so there are lots of reasons why people should stop smoking. Lack of exercise can increase risk for cancers, as can obesity, excessive alcohol consumption and excessive sun exposure. And certain medications, such as hormones, may increase risk of cancer. While there may be some risk factors that we may not be able to modify, these are all risk factors that we can modify and should try to do so.

How should people try to understand research as additional studies are conducted?

I really think that when studies like the recent study from Taiwan are published, they are important. But I think they need to be looked at alongside all related studies that have been done. And when there are conflicting results, it is a good indication that more research is needed. I think when people have questions about studies that have been done, they should discuss them with their health care provider.


Costello, Kathleen, MS, ANP-BC, MSCN. Telephone interview. 19 Feb. 2014.

E. Kingwell, C. Bajdik, N. Phillips, F. Zhu, J. Oger, S. Hashimoto, H. Tremlett.Cancer risk in multiple sclerosis: findings from British Columbia, Canada**.** Brain, 2012; DOI: 10.1093/brain/aws148

Hughes, Sue. "Multiple Sclerosis Linked to Higher Cancer Risk." Medscape. Medscape, 28 Jan. 2014. Web. 20 Feb. 2014.