Multiple sclerosis (MS) patients appear to have a lower cancer risk, according to a new study led by researchers at the University of British Columbia and Vancouver Coastal Health.

The study, published in the current issue of the journal Brain, is the first to investigate overall cancer risk in MS patients in North America.

“Because the immune system plays important roles in both cancer and MS, we wanted to know whether the risk of cancer is different for people with MS,” says Elaine Kingwell, the study’s lead author and a postdoctoral fellow in the UBC Faculty of Medicine and Brain Research Centre at UBC and VCH Research Institute. “Not only did MS patients have a lower overall cancer risk, the risk for colorectal cancer in particular was significantly lower.”

The researchers compared the diagnoses of cancer in MS patients in British Columbia with those of the general population. While they found that MS patients have a lower risk in general for cancer – and in particular for colorectal cancer – they found that the risks for brain cancer and bladder cancer were slightly elevated (albeit not significantly). In patients with relapsing-onset MS, the risk for non-melanoma skin cancer was significantly greater.

Further studies will be needed to understand the reasons for this reduced overall cancer risk.

An unexpected finding was that for those who did develop cancer, tumour size tended to be larger at time of diagnosis. More work is needed to determine why some tumours might be caught later in people with MS.

“Because the symptoms of MS can be broad and include feelings of fatigue, it’s possible the symptoms of cancer are being masked or overlooked,” says Helen Tremlett, the study’s senior author and an associate professor in the UBC Faculty of Medicine. She adds that, regardless of the findings, MS patients and their physicians are encouraged to follow cancer screening guidelines. Her team is planning a follow up study to determine whether death rates due to cancer are altered in MS patients.