Mar 30, 2009
New Study Reports Reduced Overall Cancer Risk in People with MS
Swedish researchers report that risk for several types of cancers was reduced in people with MS, but that the risk for brain tumors and urinary cancer was increased, in a study of more than 20,000 people with MS compared with more than 200,000 controls without MS. Shahram Bahmanyar, MD, PhD and colleagues (Karolinska Hospital, Stockholm, Sweden) report their findings in Neurology (2009;72:1170–1177). The reasons for these findings are unclear, but the study serves as a reminder to both people with MS and their health care providers of the need for keeping careful watch over overall health.
Background: Multiple sclerosis occurs when the immune system attacks and damages the brain and spinal cord. Epidemiologic studies involve the study of patterns of disease occurrence in people with MS in order to discover the risk factors for getting MS, and to understand their lifetime with the disease. Several epidemiologic studies have examined whether cancer risk is increased in people with MS, with conflicting results.
The Study: Investigators estimated cancer risk among 20,276 people with MS and 203,951 controls without MS, as well as among 11,284 fathers and 12,006 mothers of participants with MS, compared with 123,158 fathers and 129,409 mothers of controls. Participants were identified using several national registries, including the national Swedish MS Register and Swedish Cancer Register. Participants’ records were reviewed from 1958, when the Cancer Register was established, until diagnosis of cancer, death, emigration, or December 31, 2005.
The risk of cancer (overall and specifically including cancers of the stomach, pancreas, lung, ovary, prostate, and lymphoma) was reduced by about 10% in people with MS compared to controls, particularly among women. However, the investigators also found that the risk of brain tumors and urinary cancers was increased, noting the possibility that some of this may relate to the increased surveillance and diagnostic workups such as MRI that people with MS are more likely to have compared to those without MS, There were no increased or decreased cancer risks for parents of people with MS compared with parents of controls, arguing against any simple inherited characteristic.
The authors noted several factors that might contribute to the reduced overall risk – although the study was not designed to evaluate these factors – including as yet unidentified genes associated with MS that might protect against cancer, healthful lifestyle changes due to the MS diagnosis, treatment, or that the autoimmune attack launched in MS on the nervous system might actually serve as a ‘tumor defense mechanism.’
Comment: “This study adds solid findings to an important topic,” says John Richert, MD, Executive Vice President for Research & Clinical Programs for the National MS Society. “We have to look at all aspects of the lives of people with MS, not just the disease itself.
“Dr. Bahmanyar’s team was able to complete this study because of Sweden’s extensive registries. This is the kind of information that we need to gather in the U.S. to confirm and explore these findings further, e.g., why were most cancers reduced? Why were some risks increased? Our efforts to establish a permanent national MS and Parkinson’s registry will undoubtedly help us here.”
Read more about how people with MS and their physicians can manage all aspects of a healthy life with MS, and how activists can help to increase MS research, specifically by encouraging congress to legislate a national registry to improve MS epidemiology research.