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‘Reassuring’ data on cancer risk in people with multiple sclerosis

Reuters Health - 25/11/2020 - People with multiple sclerosis (MS) are at increased risk of developing bladder cancer but not breast or colorectal cancer, according to a large study from Canada.

"This is good news for people with MS, because earlier studies have shown a link between MS and breast and colorectal cancers," said study author Dr. Ruth Ann Marrie of the University of Manitoba, in Winnipeg, in a news release.

However, there was an increased risk for bladder cancer in people with MS. This may have to do with the fact that people with MS are more likely to have urinary-tract infections and use catheters.

"I do think the data are broadly reassuring for patients," Dr. Marrie told Reuters Health by email.

"Prior studies have had somewhat variable results - likely in part due to differing methods and smaller sample sizes. This study was larger than previous studies, enhancing the precision of our estimates," she said.

Using population-based administrative data, the researchers identified almost 54,000 people with MS and matched each one of them to five controls without MS. They used cancer registries to estimate incidence of breast, colorectal, bladder and 12 other cancers among study participants.

On multivariable analysis, adjusting for age at the index date, SES, region, birth cohort, and comorbidity, there was no difference in breast-cancer risk between patients with and without MS (pooled hazard ratio, 0.92; 95% confidence interval, 0.78 to 1.09). The same was true for colorectal cancer (pooled HR, 0.83; 95% CI, 0.64 to 1.07).

Mortality rates for breast and colorectal cancer also did not differ between MS patients and controls.

The findings were consistent across two time periods - from 1998 to 2007, when disease-modifying agents such as interferon-beta and glatiramer acetate were being introduced, and from 2008 to 2017, when second-generation disease-modifying agents, including natalizumab, dimethyl fumarate, fingolimod, teriflunomide and alemtuzumab, were introduced.

There was a higher incidence of bladder cancer in people with MS (incidence rate ratio, 1.72; 95% CI, 1.28 to 2.30).

Strengths of the study include the large sample size across two Canadian provinces, yielding greater statistical power than prior studies. "Both provinces have comprehensive, high quality, population-based administrative (health claims) data and cancer registries. As these data are collected prospectively they are not subject to recall bias," the authors note in their report in Neurology.

Although the results were adjusted for multiple medical conditions, the authors were unable to account for differences in health behaviors such as smoking, diet and physical activity. Also, the study did not account for the possibility of specific MS-modifying therapies contributing to peoples’ cancer risk.

The study was supported by the MS Society of Canada.

SOURCE: https://bit.ly/399RXvW Neurology, online November 25, 2020.

By Megan Brooks

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