Researchers gathered and reviewed 10 years of data from the French national healthcare database for the study. A total of 140,649 individuals with MS were identified and matched with controls based on factors such as age, gender, insurance, and residence to 562,596 individuals without MS.
All participants were cancer-free 3 years before the study and followed for an average of 8 years. During the study period, 8,368 individuals with MS and 31,796 individuals without MS developed cancer.
The results revealed that over the follow-up period of 8 years, the incidence of cancer was 799 per 100,000 person-years in people with MS and 736 per 100,000 person-years in matched controls. Moreover, individuals with MS had a 6% greater risk of developing any cancer type compared with individuals without MS, and the correlation was primarily observed in women (HR [hazard ratio], 1.08; 95% CI, 1.05-1.11).
With regard to specific types of cancer, the researchers discovered that compared with those without MS, patients with MS had a 71% increased risk for bladder cancer (HR, 1.71; 95% CI, 1.54-1.89); a 68% increased risk for brain cancer (HR, 1.68; 95% CI, 1.42-1.98); and a 24% augmented risk for cervical cancer (HR, 1.24; 95% CI, 1.12-1.38).
However, in contrast, those with MS had a 20% lower risk for prostate cancer (HR, 0.8; 95% CI, 0.73-0.88); a 10% lower risk for colorectal cancer (HR, 0.9; 95% CI, 0.84-0.97); and a 9% lower risk for breast cancer (HR, 0.91; 95% CI, 0.86-0.95) versus those without MS.
The results also revealed that the risk for cancer was greater among patients with MS who were aged younger than 55 years (HR, 1.2; 95% CI, 1.15-1.24) but lower in those aged 65 years and older (HR, 0.89; 95% CI, 0.85-0.94) compared with people without MS, and this correlation was observed in all cancer locations.
“Cancer risk was slightly increased in PwMS, particularly for urogenital cancers, possibly due to surveillance bias. Risk fluctuated depending on age, perhaps due to varying generational screening practices (i.e., diagnosis neglect in the older PwMS) and risk factors,” the authors concluded.
Study author Emmanuelle Leray of Rennes University in France stated, “People with MS undergo an increased number of tests to monitor MS, making it more likely to detect other diseases. We found an association between some types of cancer and MS, which may have different explanations depending on a person’s age and the type of cancer. Overall, our study found the increased risk of cancer was quite small.
“While our study found a higher risk for brain cancer, it may be due in part to earlier detection in those with MS since they regularly have brain scans which may detect cancers earlier before a person has symptoms,” stated Dr. Leray. “Frequent urinary tract infections in people with MS and the use of immunosuppressant drugs may contribute to their higher risk of bladder and cervical cancers.”
Dr. Leray also noted, “The lower risk for colorectal and breast cancers may be due in part to fewer people with MS getting screened for cancer in older age when they may be experiencing more MS symptoms. More research is needed, including studies that look at more closely at how cancer screenings may play a role.”
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