This is one piece of good news.
For reasons that are unclear, patients with multiple sclerosis (MS) appear to be less prone to develop cancer in general than other individuals.
“We speculate that the lower risk for cancer among people with MS could be a result of lifestyle changes or treatment following diagnosis,” lead author Dr. Shahram Bahmanyar, of the Karolinska Institute in Sweden, said in a statement.
“The increase in brain tumor diagnoses may be due to brain inflammation,” Dr. Bahmanyar added, “but this finding may not reflect a real increase in cancer risk, as there is some evidence that more frequent neurological investigations in these patients mean that brain tumors are more likely to be found sooner. There may also be reasons related to the disease that could increase the risk for urinary organ cancers, resulting from chronic irritation to those organs as a result of MS.”
The authors found no increased or decreased cancer risk in the parents of the MS patients, suggesting that a simple inheritance characteristic is unlikely to account for the association seen in the study group.
The findings, reported in the March 31st issue of Neurology, stem from a study of 20,276 patients with MS and 203,951 subjects from the Swedish general population. Data from the parents of subjects in both groups were also analyzed. The average follow-up period was 35 years.
MS was associated with a 9% reduction in the overall cancer risk, the authors found. As noted, MS increased the odds for brain tumors and urinary organ malignancies — by 44% and 27%, respectively.
While the relative risks of certain cancers are increased, Dr. Bahmanyar emphasized that the absolute risk is small. For example, with urinary organ cancer, “less than 0.2% of people with MS developed this cancer for every 10 years of follow-up.”