Abstract
PURPOSE: To characterize the effects of formulary changes and governmental safety warnings on use of erythropoiesis-stimulating agents (ESAs) in patients with cancer. PATIENTS AND METHODS: We conducted a cross-sectional time-series analysis using health administrative data from Ontario, Canada. From January 1997 to December 2009 we identified all ESA initiations among patients diagnosed with cancer. We explored the effects of two formulary changes that progressively liberalized coverage for ESAs, first by rescinding the requirement for blood transfusion in 2003 and then by removing all restrictions in 2007. We also explored the effect of US Food and Drug Administration and Health Canada warnings issued in the second quarter of 2007. To assess regional variability in ESA use, we determined prescription rates for each of Ontario's 14 regional cancer centers. RESULTS: After the first formulary change, the ESA initiation rate increased to 1.66 new users per 1,000 patients with cancer, 374% more than predicted (P < .001). After the second formulary change, the initiation rate increased to 3.97 new users per 1,000 patients with cancer, 73% more than predicted (P < .001). After the safety warnings, this rate declined 81% by study end (P < .001). We found significant regional variation in ESA use. CONCLUSION: Formulary access and safety warnings had significant impacts on the new use of ESA drugs in patients with cancer. This suggests that both are effective means of influencing the use of these drugs. Variable ESA prescription rates across our region may reflect a lack of consensus regarding their utility.