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Multiple Sclerosis Doesn’t Seem To Affect Breast Cancer Survival

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Women who are diagnosed with multiple sclerosis and breast cancer have about the same risk of dying from breast cancer as women who are diagnosed with only breast cancer, according to a Canadian study.

Still, women diagnosed with multiple sclerosis and breast cancer were more likely to die from any cause than women diagnosed with only breast cancer.

The research was published online on May 19, 2021, by the journal Neurology. Read the abstract of “Breast Cancer Survival in Multiple Sclerosis: A Matched Cohort Study.”

About multiple sclerosis
About the study
What this means for you

About multiple sclerosis

Multiple sclerosis, commonly called MS, is a disease of the central nervous system that disrupts the flow of information in the brain and between the brain and the body. In MS, the immune system attacks the protective cover around nerve fibers, called myelin, which is what causes the communication problems between the brain and the rest of the body. Eventually, the disease can cause the nerves to be permanently weakened or damaged.

The symptoms of MS vary and depend on which nerves are damaged and how much damage there is. There is no cure for MS, but treatments can help slow the progression of the disease and manage its symptoms.

The U.S. Food and Drug Administration (FDA) approved a medicine called Ocrevus (chemical name: ocrelizumab) in 2017 to treat MS.

One of the serious side effects of Ocrevus is an increase in the risk of some cancers, including breast cancer. Several people developed breast cancer while participating in clinical trials of Ocrevus.

The researchers who did this study wanted to see if there were differences in survival rates after breast cancer between women who had MS and women who didn’t have MS.

“Although multiple sclerosis and its complications remain the most common cause of death in people with MS, cancer is the second or third most common cause of death,” Ruth Ann Marrie, M.D., Ph.D., of the University of Manitoba, said in a statement. “Our study looked at whether survival rates for women after a breast cancer diagnosis [were] different for those with MS and those without it.”

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About the study

This study was a case-control study. This means that the researchers compared two groups of people: One group had MS and the other group didn’t have MS. But otherwise, the two groups were as similar as possible in terms of a number of factors, including age, breast cancer stage, and sex.

The researchers used information from medical databases to identify women diagnosed with both MS and breast cancer and similar women diagnosed with only breast cancer. The women were diagnosed between 1994 and 2016 and lived in the Canadian provinces of Manitoba and Ontario.

For each woman diagnosed with MS and breast cancer, the researchers matched her information with four women diagnosed with only breast cancer. The women were matched based on:

  • the year they were born
  • the year they were diagnosed with breast cancer
  • the region where they lived

Overall, 779 women in the study were diagnosed with MS and breast cancer and 3,116 women were diagnosed with only breast cancer.

Other characteristics of the women in the study included the following:

  • most were diagnosed with stage I or stage II breast cancer (70%)
  • their average age at breast cancer diagnosis was about 58
  • about half were diagnosed with breast cancer in 2010 or later
  • most lived in urban areas

The researchers took into account a number of factors that could affect the women’s survival after being diagnosed, including:

  • how old they were when they were diagnosed with breast cancer
  • their socioeconomic status
  • other health issues the women had
  • when they were diagnosed with breast cancer

The analysis showed that 10 years after being diagnosed with breast cancer, women diagnosed with MS and breast cancer were 28% more likely to die from any cause than women diagnosed with only breast cancer.

When the researchers looked only at deaths caused by breast cancer, they found no differences between the two groups of women.

The researchers noted that they didn’t have information about the women’s race and ethnicity, which are linked to differences in breast cancer survival rates.

“Because our study looked at women only in Canada, future studies are needed to confirm these findings in women in other countries, and identify the factors specifically related to MS that are associated with worse outcomes,” Dr. Marrie said.

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What this means for you

If you’ve been diagnosed with MS and breast cancer, this study offers some good news: Your risk of dying from breast cancer isn’t any higher than a woman who has breast cancer, but doesn’t have MS.

Still, the results showing that women diagnosed with MS and breast cancer are more likely to die from any cause are troubling.

This study only looked at survival statistics, so it’s not clear which factors specifically related to MS may be linked to worse outcomes. The researchers concluded that additional studies are needed to identify these factors so they can be treated or dealt with in another way.

Stay tuned to Breastcancer.org Research News for the latest updates on MS and breast cancer.

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Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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