Abstract
PURPOSE: The use of anticancer drugs (chemotherapies) is an important determinant of national spending trends. Recent policies have aimed to accelerate generic entry among chemotherapies to generate cost savings. METHODS: We examined the effects of generic entry on the choice of chemotherapy for the treatment of metastatic colorectal cancer (MCRC) between 2006 and 2009 using autoregressive-moving average modeling with case control. A nationally representative sample of oncologists and patients with cancer (age ≥ 65 years) was employed to estimate the magnitude and significance of the impact of the generic entry of irinotecan in February 2008 on the number of administrations of irinotecan compared with oxaliplatin. RESULTS: The generic entry of irinotecan resulted in a 17% to 19% decrease (P < .001) in use among elderly patients with MCRC compared with oxaliplatin. The results were robust to multiple sensitivity checks. CONCLUSION: This study provides novel and robust estimates of the decline in use of a chemotherapy to treat a common cancer in the elderly after patent expiration. The results suggest estimates from a previous Office of the Inspector General report of the potential savings derived from the generic entry of irinotecan for public payers are an overestimate, likely confounded by oncologists' response to financial incentives, changes in scientific evidence, and promotional activities. As calls for improving the quality and cost efficiency of oncology increase, future empirical work is needed to examine the responsiveness of oncologists' treatment decision making to incentives among patients of all ages and insurance types.