Some cancer types may be slightly more prevalent among patients with multiple sclerosis compared with those without the condition, according to a recent study published by Pierret et al in Neurology.
Background
In multiple sclerosis, the body’s immune system attacks myelin, the fatty white substance that insulates and protects the nerves. The condition is chronic and can be unpredictable and disabling.
“People with [multiple sclerosis] undergo an increased number of tests to monitor [their disease], making it more likely to detect other diseases,” explained senior study author Emmanuelle Leray, PhD, of Rennes University in France. “We found an association between some types of cancer and [multiple sclerosis], which may have different explanations depending on a [patient’s] age and the type of cancer. Overall, our study found the increased risk of cancer was quite small,” she added.
Study Methods and Results
In the recent study, investigators analyzed used 10 years of data from the French national health-care database to identify 140,649 patients with multiple sclerosis. They then matched the patients with 562,596 individuals without multiple sclerosis on the basis of age, sex, and residence. All of the participants were cancer free 3 years prior to the study.
After an average follow-up of 8 years, the investigators found that 8,368 of the patients with multiple sclerosis and 31,796 of the individuals without the condition developed cancer. They determined that there were 799 cancers per 100,000 person-years among the patients with multiple sclerosis and 736 cancers per 100,000 person-years among those without the condition. Person-years represent both the number of study participants and the amount of time each individual spends in the study.
The patients with multiple sclerosis had a 6% increased risk of developing any type of cancer regardless of age, sex, or residence. The cancer risk was higher among those under 55 years and lower in those 65 years and older compared with individuals without multiple sclerosis.
Additionally, patients had a 71%, 68%, and 24% increased risk of developing bladder cancer, brain cancer, and cervical cancer, respectively. However, the risk of prostate cancer was 20% lower, the risk of colorectal cancer was 10% lower, and the risk of breast cancer was 9% lower among the patients with multiple sclerosis.
Conclusions
Although the findings didn’t prove that multiple sclerosis increased a patient’s risk of cancer, they did demonstrate an association between the condition and cancer risk. The investigators noted that a study limitation involved their inability to adjust for factors such as education, income, smoking, and alcohol consumption because this information was not available in the national database.
“While our study found a higher risk for brain cancer, it may be [caused] in part [by] earlier detection in those with [multiple sclerosis], since they regularly have brain scans [that] may detect cancers earlier, before a [patient] has symptoms. Frequent urinary tract infections in [patients] with [multiple sclerosis] and the use of immunosuppressant drugs may contribute to their higher risk of bladder and cervical cancers,” indicated Dr. Leray. “The lower risk for colorectal and breast cancers may be [caused] in part [by] fewer [patients] with [multiple sclerosis] getting screened for cancer in older age when they may be experiencing more [multiple sclerosis] symptoms. More research is needed, including studies that look more closely at how cancer screenings may play a role,” she concluded.
Disclosure: The research in this study was supported by the Rennes Institute of Clinical Neurosciences and the EDMUS-ARSEP Foundation. For full disclosures of the study authors, visit neurology.org.
