Background: Sunitinib and pazopanib are among the most prescribed targeted therapies for the systemic management of advanced renal cell carcinoma (RCC), but published cost comparisons between the 2 agents are few and limited by methodological and population differences. Also, sunitinib is administered on a 4-week on/2-week off cycle, and pazopanib is taken continuously. Thus, appropriate use and cost comparisons between the 2 drugs require methodological approaches to account for these differences. One way to accomplish this is to substitute expected for observed days supply. Recognizing the effects of nonrepresentative days supply values is important for assessing real-world treatment patterns and costs.
Objectives: To (a) characterize demographic and clinical characteristics among patients with RCC newly initiating sunitinib or pazopanib, using a large administrative claims dataset; (b) characterize treatment patterns, persistence, and costs for each treatment group; and (c) assess the effect on treatment patterns and costs for sunitinib by substituting 42 days for prescriptions with 28- or 30-day supplies to account for sunitinib's 4-week on/2-week off dosing schedule.
Methods: This was a retrospective cohort study using health care claims data from the Truven MarketScan Research Databases, which include enrollment information and medical and pharmacy claims. Baseline patient demographic and clinical characteristics and treatment patterns (continuation, discontinuation, switching, or interruption; days supply; and persistence) were compared. Health care costs were calculated as mean daily index medication costs and as total, medical, and medication (all-cause and RCC-related) costs over the 12 months post-index period. Inclusion criteria were continuous health plan enrollment between 6 months pre-index and 12 months post-index; no RCC medications 6 months pre-index; ≥ 2 RCC diagnoses within ±180 days of index; and age ≥ 20 years. For demographic and clinical characteristics, treatment patterns, and costs, means (± standard deviations) for continuous data and relative frequencies for categorical data were reported. Chi-square tests or Student t-tests were used to evaluate differences other than costs. A generalized linear model with gamma distribution and log link was used for evaluating costs, controlling for patient demographic and pre-index clinical characteristics, persistence days, and index medication. All statistical tests were 2-tailed with significance set at P < 0.05 for all comparisons except for interactions with significance set at P < 0.10. The effects of substituting 42 days supply for sunitinib prescription records with 28 or 30 days supply were determined.
Results: In total, 609 (15.1% of the sunitinib overall sample) sunitinib patients and 183 (8.3% of the pazopanib overall sample) pazopanib patients were included. Demographic and clinical characteristics were similar for each treatment cohort. The persistence periods and number of prescriptions filled were also similar. Without substitution, significant differences were observed between treatment groups in patterns of index medication use (overall P = 0.0409), with fewer patients taking sunitinib continuing treatment than patients taking pazopanib. However, with substitution, treatment patterns differed significantly (overall P = 0.0026), but with more sunitinib patients than pazopanib patients continuing treatment. Without substitution, unadjusted daily mean index medication costs were significantly different for sunitinib ($216) versus pazopanib ($177, P < 0.0001). Substitution of sunitinib days supply eliminated the significant differences in daily index medication costs between treatment groups. The 1-year RCC-related and all-cause medication, medical, and total unadjusted costs were not significantly different between treatment groups, and substitution had no effect on these costs. After adjustment for possible confounding factors, these cost results were similar to those found with unadjusted analyses.
Conclusions: In this study, patients with RCC who were initiating sunitinib and pazopanib had similar demographic and clinical characteristics and drug persistence patterns. The effect of substituting days supply values was demonstrated as an approach to considering differences in dosing cycles. Substitution significantly reduced sunitinib mean daily index medication costs and eliminated or reversed the direction of significant differences in costs between drugs during the persistence period. No significant differences were observed in unadjusted or adjusted 1-year costs.
Disclosures: This study was funded and conducted fully by Pfizer. All authors are employees of Pfizer. This work was presented in part as posters at the 2015 Genitourinary Cancers Symposium, of the American Society of Clinical Oncology; Rosen Shingle Creek, Orlando, FL; February 26-28, 2015, and the 20th Annual International Meeting of the International Society for Pharmacoeconomics and Outcomes Research; Philadelphia, PA; May 16-20, 2015. All authors contributed to study concept and design and to data interpretation. Mardekian was primarily responsible for data collection, along with Harnett. MacLean and Harnett worked on the manuscript, which was revised by MacLean and Mardekian.