Boosting Molecular Testing in Patients with GIST Would Have Minimal Cost Impact, Study Finds

An increase in molecular testing of patients with gastrointestinal stromal tumors (GIST) would allow physicians to make better therapeutic decisions without a significant uptick in the cost of care, according to a new analysis.

The research found that increasing molecular testing rates to 100% among patients with 2 mutation types would result in an overall cost increase of just $15,213 per million members of a managed care plan per year. That breaks down to just 1.5 cents per member, per year, wrote corresponding author David Proudman, M.P.H., of the Analysis Group economic consulting firm.

The research was set to be unveiled at the Academy of Managed Care Pharmacy’s 2020 annual meeting. The in-person event was canceled because of COVID-19, but the research was posted online instead.

Over the past two decades, investigators have learned how to fine-tune therapy for patients with GIST by matching them with therapeutic strategies tied specifically to the mutations behind their cancers. Yet such “precision medicine” is far from universal. “The use of molecular diagnostics to classify GIST has been shown to be successful in optimizing patient treatment, but these methods remain under-utilized,” wrote Michael C. Heinrich, M.D., of the Oregon Health and Science University and his co-authors in a 2017 review paper.

Proudman and colleagues decided one way to encourage more physicians to follow molecular testing guidelines would be to calculate the costs of including the testing in a patient’s care. To do so, he and colleagues set up a cost-impact model looking at how universal (100%) molecular testing of patients with GIST associated with mutations of PDGFRA exon 18 and KIT exon 9 would affect the overall cost to insurers. At present, an estimated 60% of patients with KIT exon 9 mutations undergo molecular testing, and just 49% of those with PDGFRA exon 18 mutations are tested.

The model assumed that patients with other types of mutations, and those for whom testing was not performed, received the standard therapy of imatinib (Gleevec) 400mg. Those with KIT exon 9 mutations were assumed to receive a higher, 800 mg dose of imatinib in the model. Those with PDGFRA exon 18 mutations were modeled based on receiving best supportive care, since an effective therapy has yet to be found for patients with the most common of these mutations.

The model assumed the bulk of patients (69%) were on commercial insurance plans; the remaining patients in the simulation were assumed to be on Medicare (23%) and Medicaid (9%). The rate of GIST cases in the study was set at 11 per million members.

As noted above, increasing molecular testing rates to 100% for these patients increased the cost per million members per year by just more than $15,000. Within that number were a mix of increased and decreased costs. Testing costs increased by $2,748, but adverse event costs were $293 lower.

The main influence of the overall increased cost were pharmacy costs, which rose $12,758. Proudman and colleagues said the higher pharmacy costs were due to higher dosages among patients with KIT exon 9 mutation, as well as increased duration of therapy for those patients because of longer progression-free survival. If patients with KIT exon 9 mutations were excluded, overall costs would actually drop slightly due to the decision to treat patients with PDGFRA exon 18 mutations with best supportive care instead of the standard 400 mg dose of imatinib.

Proudman and colleagues said the cost increases were minimal regardless of plan type.

“Increased molecular testing in GIST is associated with minimal additional costs and a meaningful increase in the number of patients receiving optimized treatment,” Proudman and colleagues concluded.