Having MS may marginally increase likelihood of cervical cancer: Study

There’s no evidence to suggest that multiple sclerosis (MS) directly causes most cancers, but having the condition may marginally increase the likelihood of developing cervical cancer, according to a new study from China.

That study found “no causal relationship between MS and 15 types of cancers except cervical cancer,” the researchers wrote.

However, the team stressed that their “robust” analysis “showed that MS was only associated with a marginal increased risk of cervical cancer.”

The study, “Association between multiple sclerosis and cancer risk: A two-sample Mendelian randomization study,” was published in PLOS One.

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MS occurs when the immune system wrongly attacks the protective covering of nerve fibers in the brain and spinal cord, leading to a range of symptoms. It remains unclear why this happens, but it may be caused by a combination of environmental and genetic factors.

Research on MS and cancer has shown mixed results. While some studies suggest MS may protect against cancer, others show it may increase the risk for such diseases.

Now, a team from the Sun Yat-sen University Cancer Center, in Guangzhou, turned to Mendelian randomization to better assess the causal effect of MS in cancer — without potential confounding factors that could influence the results. A confounding factor is an unmeasured variable that influences both the supposed cause and effect in a study.

Mendelian randomization is a type of analysis that uses genetic variations as proxies for an exposure of interest — in this case, genetic variations linked with a greater susceptibility to multiple sclerosis as proxies of MS — to investigate the association between the exposure and an outcome.

If there is a causal relationship between the two, then that association should also be observed between the genetic variants tied to greater MS susceptibility and cancer.

Genetic data related to MS came from more than 115,000 samples from the International Multiple Sclerosis Genetics Consortium, while cancer data came from the U.K. Biobank, a database of genetic and health information from more than 500,000 volunteers.

Overall, the researchers identified 107 single nucleotide polymorphisms (SNPs), or variations at a single position in the DNA, that were strongly linked to MS. However, five were linked to smoking and the Epstein–Barr virus, which are risk factors for both MS and cancer, and were thus excluded from the analysis.

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The researchers then sought to determine if the 102 SNPs that remained were associated with any of the 15 cancers registered in the U.K. Biobank. These included cancers of the prostate, breast, bladder, brain, cervix, throat, liver, and lung. Other types, such as ovarian, colorectal, and melanoma (a skin cancer) also were included.

The results showed no causal link between MS and most cancers — 14 specifically.

There was, however, a “marginal” increase in the likelihood of cervical cancer — by 0.04% — in people with MS variants compared with individuals who lacked these genetic variations, the researchers found.

The intricate biological mechanisms underpinning this relationship remain elusive and warrant further exploration.

The scientists wrote that they “suspect that the occurrence of premalignant conditions and cervical cancer might be associated with the drugs used in MS treatment.” But, the team noted that more research is needed to better understand this link.

“The intricate biological mechanisms underpinning this relationship remain elusive and warrant further exploration,” they wrote.

Overall, the team concluded, “This study reveals that MS is only causally associated with a marginal increased risk of cervical cancer and shows no association with other types of cancer.”