In sensitivity analyses using the commonly accepted cost–effectiveness benchmark range of $50,000−$100,000/QALY, the results were sensitive to changes in the overall emesis control rates for the onda-based two-drug strategy. If the probability of overall emesis control for the onda-based two-drug strategy was as low as its estimated lower bound (46%), the ICER for the palo-based two-drug treatment alternative would drop to $53,892/QALY. The results were also sensitive to changes in the effectiveness for the palo-based two-drug regimen: When its overall control rate was as high as its estimated upper bound (86%), its ICER would be $71,472. In contrast, the results were not sensitive to variations in the probability of overall emesis control for the three-drug strategies, nor were they sensitive to changes in the relative probability of emesis control in subsequent cycles of AC for either the two- or three-drug strategies.
If the probability of emesis-related hospitalization was as high as the upper limit of its 95% confidence interval (CI), the ICER for the palo-based two-drug regimen would be $97,301/QALY. However, changes in the cost of an emesis-related admission (95% CI $3,921−$6,112) did not significantly alter the results, nor did variations in office visit and rescue medicine utilization and their associated costs. The results were also not sensitive to variations in the values for the utility weights throughout their 95% CIs. We performed a threshold analysis to explore the price per dose of palo that would result in an acceptable cost–effectiveness ratio under the $100,000/QALY benchmark and found that the ICER for the palo-based two-drug treatment alternative would only fall to a $100,000/QALY threshold when the cost of palo is decreased by 11%.
Figure 2 shows the cost–effectiveness acceptability curves for each strategy, with the onda-based two-drug therapy as the base comparator. These curves show the proportion of the 100,000 simulations in which the comparing antiemetic regimen was considered more cost-effective than the base comparator at different thresholds. Using the benchmark of U.S. $100,000/QALY, the palo-based two-drug strategy and the two-drug regimen plus aprepitant following the onset of emesis were shown to be cost-effective in 39% and 26% of the simulations with the onda-based standard therapy as the baseline, respectively, whereas the palo-based and onda-based three-drug strategies and the onda-based two-drug regimen with aprepitant after emesis were cost-effective in fewer than 10% of the simulations. Of note is that the slope of the acceptability curves for the palo-based two-drug strategies are steep when willingness to pay exceeds $50,000/QALY, indicating that the greater the threshold, the greater the increase in the level of confidence that these strategies could be cost-effective. For example, the probability that the palo-based two-drug strategy is more cost-effective than the onda-based two-drug strategy rises to 51% at a threshold value of $125,000/QALY and exceeds 60% at $150,000/QALY.