Cost-effectiveness Analysis of Olanzapine in Four-drug Antiemetic Therapy in Japanese Patients Treated with Highly Emetogenic Cisplatin-containing Chemotherapy

Background: Olanzapine has been shown to have an additive effect on the three-drug antiemetic therapy consisting of aprepitant, palonosetron, and dexamethasone, in a highly emetogenic cisplatin-containing chemotherapy. Although olanzapine may be more economical than aprepitant or palonosetron, an adequate cost-efficacy analysis has not been conducted.

Methods: We conducted a cost-utility analysis to evaluate the cost-effectiveness of olanzapine use in four-drug antiemetic therapy among Japanese patients. We simulated model patients treated with highly emetogenic cisplatin-containing chemotherapy and developed a decision-analytical model of patients receiving triple antiemetic therapy with or without olanzapine in an inpatient setting. The cost and probabilities of each treatment were calculated from the perspective of the Japanese healthcare payer. The probabilities, utility value, and other costs were obtained from published sources. One-way and probabilistic sensitivity analyses were conducted to examine the influence of each parameter on the model and the robustness of a base-case analysis. Threshold analysis was conducted to determine the cost of olanzapine that would make the incremental cost-effectiveness ratio (ICER) equivalent to the threshold ICER). The threshold incremental cost-effectiveness ratio was set at 5 million Japanese Yen (JPY) per quality-adjusted life-year (QALY) gained.

Results: The cost was 10,238 JPY in the olanzapine regimen and 9719 JPY in the non-olanzapine regimen. The QALY gained were 0.01065 QALYs and 0.01029 QALYs in the olanzapine and non-olanzapine regimen, respectively. The incremental cost of the olanzapine regimen relative to the non-olanzapine regimen was 519 JPY, and the incremental QALYs were 0.00036 QALY, resulting in an ICER of 1,428,675 JPY per QALY gained. In the one-way sensitivity analysis, the results were most sensitive to the utility value of incomplete control. The probabilistic sensitivity analysis revealed the probability that the ICER was below the willingness-to-pay, and the incremental QALYs was positive was 96.2%. The calculated cost of olanzapine per 5 mg that would make the incremental cost-effectiveness ratio equivalent to the threshold incremental cost-effectiveness ratio was calculated to be 475 JPY.

Conclusions: Olanzapine was cost-effective in the four-drug antiemetic therapy for Japanese patients treated with highly emetogenic cisplatin-containing chemotherapy.