Impact of intravenous cancer drug wastage on economic evaluations.

Abstract

6607 Background: Intravenous drugs administered through body-surface area (BSA) or weight-based dosing may cause wastage due to large and/or limited fixed vial sizes, and vial sharing restrictions. Drug wastage leads to incremental costs without incremental value to patients. Bach et al. (2016) estimated 10% of revenue ($1.8 billion) from cancer drugs would result from wastage in 2016. The pan-Canadian Oncology Drug Review (pCODR) committee provides recommendations on which drugs to publicly reimburse by reviewing clinical and economic evidence. There is considerable potential that drug wastage could impact the economic evaluations. We sought to determine the impact of modeling cancer drug wastage on the results of economic evaluations. Methods: Economic evaluations submitted by drug manufacturers and reviewed by the pCODR Economic Guidance Panel (EGP) were assessed for frequency of wastage reporting and modeling. Cost-effectiveness analyses and budget impact analyses were conducted for scenarios in which “no wastage” and “wastage” of drugs occurred. Sensitivity analyses were performed to determine the effects of BSA and weight variation. Results: 12 drugs for use in 17 indications were analyzed. Wastage was reported in 71% and incorporated in 53% of manufacturer’s models, resulting in a mean incremental cost-effectiveness ratio (ICER) increase of 6.1% (range: 1.3% to 14.6%). EGP reported and incorporated wastage for 59% of models, resulting in a mean ICER increase of 15.0% (2.6% to 48.2%). When maximum wastage (i.e. the entire unused portion of each vial is discarded) was incorporated in our independent analysis, the mean ICER increased by 24.0% (0.0% to 97.2%) and the mean 3-year total incremental costs increased by 26.0% (0.0% to 83.1%). Over a 3-year period, wastage can increase the total incremental drug budget cost by CAD $102 million nationally. Changing the mean BSA or body weight caused 45% of the drugs to use a different vial size (if available) and/or quantity, resulting in further increased drug costs. Conclusions: Wastage can have an under-recognized and significant impact on economic evaluations of intravenous chemotherapy drugs. Guidelines are needed to promote uniform and optimal modeling of drug wastage in economic evaluations.