Assessment of malignancy risk in patients with multiple sclerosis treated with intramuscular interferon beta-1a: retrospective evaluation using a health insurance claims database and postmarketing surveillance data.

ABSTRACT

BACKGROUND: Intramuscular interferon beta-1a (IFNß-1a), a multiple sclerosis (MS) therapy that has been commercially available for over a decade, provides a unique opportunity to retrospectively assess postmarketing data for evidence of malignancy risk, compared with relatively limited data available for more recently approved therapies. Postmarketing and claims data were analyzed to determine the risk of malignancy in MS patients treated with intramuscular IFNß-1a. MATERIALS AND METHODS: The cumulative reporting rates of suspected adverse drug reactions coded to malignancy in the intramuscular IFNß-1a global safety database were compared with malignancy incidence rates in the World Health Organization GLOBOCAN database. In addition, using data from a large US claims database, the cumulative prevalence of malignancy in MS patients treated with intramuscular IFNß-1a was compared with non-MS population controls, MS patients without intramuscular IFNß-1a use, and untreated MS patients. Mean follow-up was approximately 3 years for all groups, ie, 3.1 years for the intramuscular IFNß-1a group (range 0.02-6.0 years), 2.6 years for non-MS population controls (range 0-6.0 years), 2.6 years for the intramuscular IFNß-1a nonuse group (range 0.01-6.0 years), and 2.4 years for the untreated MS group (range 0.01-6.0 years). RESULTS: An estimated 402,250 patients received intramuscular IFNß-1a during the postmarketing period. Cumulative reporting rates of malignancy in this population were consistent with GLOBOCAN incidence rates observed within the general population. The claims database included 12,894 MS patients who received intramuscular IFNß-1a. No significant difference in malignancy prevalence was observed in intramuscular IFNß-1a users compared with other groups. CONCLUSION: Results from this evaluation provide no evidence of an increased risk of malignancy with intramuscular IFNß-1a use.