"After an average follow-up of 35 years, the researchers found that multiple sclerosis patients had a lower overall cancer risk (hazard ratio 0.91), although the risk was higher for cancers such as brain tumors (hazard ratio, 1.44), urinary organ cancers (HR, 1.27) and cancers of the small intestine (HR, 1.63). Cancer risk was even lower in patients diagnosed at an earlier age and in women. Overall cancer risk was similar in parents of multiple sclerosis patients and parents of patients without the disease, the report indicates.
"The reduction in cancer risk in patients with multiple sclerosis may result from behavioral change, treatment, or we speculate that some immunologic characteristics of multiple sclerosis disease activity improve antitumor surveillance," Bahmanyar and colleagues conclude. "The lack of association among parents indicates that a simple inherited characteristic is unlikely to explain the reduced cancer risk among patients with multiple sclerosis."