The effectiveness of approved therapies used to treat gastrointestinal stromal tumors (GIST) varies by mutation type. Researchers assessed the cost impact associated with an increase in molecular testing of PDGFRA exon 18 and KIT exon 9 in U.S. patients with GIST and found that this had a minimal additional cost burden but resulted in a meaningful increase in the number of patients receiving optimized treatment. The results of the study were presented during AMCP eLearning Days in a poster presentation titled “The Cost Impact of Increased Molecular Testing Rates for the Treatment of Patients with Gastrointestinal Stromal Tumors.”
Researchers created a cost impact model in Microsoft Excel with a U.S. health plan perspective on a 12-month incidence basis. The model included patients with both adjuvant and advanced/metastatic disease. The model compared costs based on current testing rates at diagnosis for PDGFRA exon 18 (49%) and KIT exon 9 (60%) and created a scenario in which 100% of patients are tested. The model incorporated testing costs assuming polymerase chain reaction-based tests.
Untested patients or those with other mutations were assumed to receive treatment with standard generic imatinib 400 mg, while patients with KIT exon 9+ mutation were assumed to receive imatinib 800 mg. Patients with PDGFRA exon 18+ mutation received best supportive care. Treatment duration in the adjuvant setting was a standard 36-month period, while treatment duration in the advanced/metastatic setting was based on median progression-free survival (PFS) from clinical trials.
The base case of the model used a mixed 69% commercial, 22% Medicare, and 9% Medicaid plan and a GIST incidence rate of 11 per one million members. The number of additional patients needed to test for one patient to receive optimized treatment was 10.
An increase in testing rates to 100% for both mutation types was associated with a total annual cost increase of $15,213 per one million members or $0.015 per-member, per-year (PMPY). Testing costs were $2,748 higher, adverse event costs were $293 lower, and pharmacy costs increased by $12,758, “driven by increased dosing and longer PFS in [patients with] KIT exon 9,” according to the researchers.
If only PDGFRA exon 18 testing were included, the cost savings would be $0.008 PMPY due to lower pharmacy costs. The magnitude of the cost impact associated with increased testing remained small across all plan types, according to the authors.
The study was sponsored by Blueprint Medicines Corporation.
Proudman D, Miller A, Nellesen D, Mankoski R, Norregaard C, Sullivan E. The Cost Impact of Increased Molecular Testing Rates for the Treatment of Patients with Gastrointestinal Stromal Tumors. Abstract C13. Presented during AMCP eLearning Days, April 20-24.