By Serena Gordon
Overall, the higher risk was small -- just 12%. However, the risk of certain cancers -- such as central nervous system (brain, spinal cord and optic nerve) cancers and urinary cancers were around 50% higher in people with multiple sclerosis (MS). And respiratory cancers were about two-thirds more likely to occur in people with MS, the study found.
The study didn't only raise concern for folks with MS, however. Seven decades of research also suggested that the siblings of people with MS who didn't have the disease themselves had about an 80% increased risk of blood cancers, such as leukemia, compared to their MS-affected siblings and people in the general population without MS.
Since siblings share both genes and environmental exposures, the researchers said their findings may indicate a shared cause between MS and cancers of the blood (hematological cancers).
Bruce Bebo, executive vice president of research for the National MS Society, said, "This is a well-done study that draws attention to a potential comorbidity of MS, but the overall risk of cancer was modest."
Bebo said the study will likely heighten people's awareness, and if it makes people more diligent about getting cancer screenings and reducing risk factors such as smoking, then it might save some lives.
But Bebo also pointed out that other research has had mixed results, with some studies that have shown a boost in cancer risk and others that haven't. Additionally, he said it's important to note that these are preliminary findings presented at a medical meeting that haven't yet been peer-reviewed.
Dr. Robert Lisak, a neurologist at Detroit Medical Center, agreed that the findings need further review. He added that this study only shows an association between cancer and MS. It does not prove a cause-and-effect relationship.
The study, led by researcher Dr. Nina Grytten, from Haukeland University Hospital, in Bergen, included data on almost 55,000 people in Norway who were born between 1930 and 1979. Almost 7,000 were people with MS, and about 9,000 were siblings of people with MS who didn't have the disease themselves. There were also almost 38,000 people who weren't related and didn't have MS themselves.
The researchers said that the increased risk of certain cancers in people with MS -- such as urinary, respiratory and central nervous system cancers -- might be due to excessive smoking in that group.
Lisak pointed out that the study included Norwegian people, so the results might be different in a more diverse population, such as the one in the United States. Also, the treatments for MS have evolved quite a bit, particularly since this information was collected.
"These are patients from a very different era in MS treatment," he said.
Because some treatments for MS affect the immune system -- even today -- Bebo said an increased risk of cancer may be a possibility.
He added that the study is a good reminder for people with MS and without to stay on top of the cancer risks you can control.
"A healthy lifestyle is important for MS, cancer, heart disease and diabetes," Bebo said.
Lisak said that quitting smoking isn't only good for lowering your risk of cancer.
"We now know that cigarette smoking is a risk factor for developing MS and smokers have an increased rate of MS progression. Don't smoke and if you do smoke, give it up," Lisak urged.
The study was presented Saturday at the European Academy of Neurology Congress in Oslo, Norway.