When cancer drug went generic, its use declined
Research Activities, December 2012, No. 388
After the patent expires for an infused chemotherapy drug and it becomes available as a generic drug, economists would predict that its use would increase. Yet a new study suggests that is not always the case. Researchers compared the use of irinotecan and oxaliplatin in elderly patients with metastatic colorectal cancer (MCRC) from 2006 through 2009. In 2008, generic irinotecan was approved by the U.S. Food and Drug Administration. After the generic entry of irinotecan into the market, the number of irinotecan administrations fell by 17 percent compared with administrations of oxaliplatin, which remained under patent protection. When the researchers added in the August 2008 decrease in Medicare reimbursement for irinotecan administration, the number of irinotecan compared to oxaliplatin administrations fell by 19 percent, and the number of patients receiving irinotecan (compared with those receiving oxaliplatin) fell by 18 percent. All of these differences were statistically significant.
The researchers conclude that estimates of savings from irinotecan becoming available as a generic were overestimated, perhaps due to financial incentives related to insurance coverage, changes in the scientific evidence to support other regimens for MCRC, and possible drug promotions by the pharmaceutical manufacturers. Their findings were based on prescribing behavior of a population-based sample of oncologists obtained from a commercial database, as well as monthly data on Medicare reimbursement rates for irinotecan and oxaliplatin. The study was funded in part by the Agency for Healthcare Research and Quality (HS18535).
More details are in "Infused chemotherapy use in the elderly after patent expiration," by Rena M. Conti, Ph.D., Meredith B. Rosenthal, Ph.D., Blase N. Polite, M.D., and others in the May 2012 American Journal of Managed Care 18(5 Spec No. 2), pp. e172-e178.