OBJECTIVES: A 2017 cost-effectiveness analysis (CEA) of cetuximab, panitumumab and best supportive care indicated neither drug was cost-effective. A patient of average height and weight (70 kg and 162 cm) was assumed to use drug quantity needed (discarding the remainder of any unused vial) but assigned an entire vial’s cost. An alternative assumption is that groups of patients are dosed together, allowing vial sharing and thereby reducing cost. As cetuximab is dosed based on a combination of height and weight - body surface area (BSA) and panitumumab by weight, this assumption and dosing differences could lead to differences in total drug cost by treatment.

METHODS: Dosing was 6mg/kg and 500mg/m² for panitumumab and cetuximab respectively. Drug costs per session were re-assessed without drug wastage and scaled to a quarterly figure to compare with original costs. This analysis is limited to drug costs per quarter for patients in the model as the interaction of drug cost with other costs in the model is complex and not yet fully determined.

RESULTS: For panitumumab the average patient needed 5 vials and wasted 80 mg. For cetuximab, 9 vials were needed (25 mg wastage). Using the wasted drug on another patient showed differential effect on the two drug costs. Per treatment, panitumumab savings were $216.34 and cetuximab’s were $41.68. Quarterly drug costs declined by $1298 and $250, respectively.

CONCLUSIONS: This research shows a potential benefit from a patient group dosing strategy which differs by drug for the average patient. It is also clear that variation from the average patient height and weight will have variable implications on total drug costs and quantitative CEA results. It is not yet clear if the qualitative CEA conclusions would vary or if treating different body type patients with different drugs based on different CEA conclusions is practical.