Cost-effectiveness of 3-years of adjuvant imatinib in gastrointestinal stromal tumors (GIST) in the United States.

BACKGROUND

Recent clinical trial data have demonstrated that 3 years vs 1 year of adjuvant imatinib therapy for patients with surgically resected Kit+ Gastrointestinal Stromal Tumors (GIST) leads to a significant improvement in recurrence-free survival and overall survival. This study assesses the cost-effectiveness of treating patients with 3 years vs 1 year of imatinib from a US payer's perspective.

METHODS

A Markov model was developed to predict GIST recurrence and treatment costs. Patients enter the model after surgery and transition among three health states: free of recurrence, recurrence, and death. Recurrence, mortality, costs, and utilities were derived from clinical trial and published literature. Expected costs and quality-adjusted life years (QALYs) were estimated and discounted at 3%/year. Deterministic and probabilistic sensitivity analyses were conducted.

RESULTS

Patients receiving 3 years of imatinib had higher QALYs (8.53 vs 7.18) than those receiving 1 year of imatinib. Total lifetime per-patient cost was $302,100 for 3 years vs $217,800 for 1 year of imatinib. Incremental cost effectiveness ratio of 3 years vs 1 year of imatinib was $62,600/QALY. Model results were sensitive to long-term rate of GIST recurrence (beyond 5 years) and cost of imatinib. At a threshold of $100,000/QALY, 3 years vs 1 year of imatinib was cost-effective in 100% of simulations.

LIMITATIONS

The model is a simplified representation of disease natural history and may not account for all possible health states and complications associated with disease. Resource utilization on treatment was estimated using the resource use data from previous trials, therefore calculated medical costs might be over-estimated compared to the real-world setting.

CONCLUSIONS

Model results suggest that treatment with 3 years vs 1 year of imatinib is cost-effective at a $100,000/QALY threshold. Clinical and economic results suggest treating surgically resected Kit+ GIST patients with 3 years of imatinib would result in improved quality-adjusted survival.