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Study found that while frequency of cancer among people with multiple sclerosis (MS) increased over time, the overall cancer risk is similar between patients with MS and the general population.
While the frequency of cancer diagnoses has increased among patients with multiple sclerosis over the past 30 years, the overall cancer risk among patients with MS and matched controls is similar, according to a study published in Journal of Neurology.
Researchers used the United Kingdom’s Clinical Practice Research Datalink, which has been collecting primary care data since 1987, to conduct a population-based nested case control study. They used the data to compare the occurrence of cancer between people with MS or clinically isolated syndrome (CIS), a single inflammatory demyelinating event that can turn into multiple sclerosis, and controls who do not have MS or CIS.
“It has been suggested that the abnormal immune response seen in MS could improve
surveillance against malignancy,” wrote the authors, led by Chiara Zecca of the Neurocenter of Southern Switzerland in Lugano, Switzerland. “However, chronic inflammation also represents a recognized risk factors for cancer development.”
The study included 10,204 patients with MS who were matched with 39,448 controls. Some of those patients were excluded from the study for various reasons, so the researchers ended up analyzing data for 9,816 patients with MS and 37,901 controls. Almost three-quarter (71.6%) of the people in both groups were women; their median age was 47. People with MS were followed up for 5.6 years after index date and the controls were followed up for 6.2 years.
Cancer was reported in 433 (4.41%) patients with MS and 2014 (5.31%) controls. Female gender was negatively associated with the risk of cancer, while age at index date and calendar year at index date were both positively associated with cancer risk. Zecca and her colleagues noted that disease status (MS vs control) was not at all associated with the risk of cancer.
The authors pointed out that a previous study in Norway had found patients with MS had an increased risk of cancer, particularly with involvement of the respiratory, urinary and central nervous system, but the MS cohort in this study did not show risk for any specific type of cancer. The findings are consistent with others from Northern Europe and Iran that found no differences in cancer risk between patients with MS and the general population. Research conducted in the United States, Canada, and Europe have found that people with MS have a lower risk of developing cancer.
The research team pointed out that while cancer risk was stable for the control group over time, the risk increased among MS patients by approximately 2% per calendar year. They hypothesized that the introduction of new therapeutic agents, changes in clinical care, standardized and regular cancer screening programs, and changes in lifestyle behaviors may explain the increase over time among patients with MS. However, they noted that this finding requires further investigation.
“While several explanations appear to be possible, including increasing surveillance and more careful cancer screening programs in MS patients, we believe the rapid and continuous evolution of MS care, treatments and related potential secondary effects, require maximal attention in routine neurological care,” Zecca and her colleagues concluded.