704P - Cost-effectiveness of three-years of adjuvant imatinib in gastrointestinal stromal tumors (GIST) in Canada

Date 30 September 2012
Event ESMO Congress 2012
Session Poster presentation II
Topics Bioethics, Legal, and Economic Issues
GIST
Presenter Anju Parthan
Authors A. Parthan1, M. Sanon1, J. Coombs2, K. El Ouagari3
  • 1Health Economics And Outcomes Research, OptumInsight, 02155 - Medford/US
  • 2Novartis Pharmaceuticals, US-07932 - Florham Park/US
  • 3Health Economics, Novartis Pharmaceuticals Canada Inc, CDN-Dorval - Quebec H9s 1A9/CA

Abstract

Background

Recent clinical trial data have demonstrated that 3 years (yrs) of adjuvant imatinib therapy for patients with surgically resected GIST leads to a significant improvement in recurrence free survival & overall survival vs. 1 yr of therapy. The objective of this study is to assess cost-effectiveness of treating with 3 yrs vs. 1 yr of adjuvant imatinib in Canada from a payer's perspective.

Methods

A Markov model was developed to predict GIST recurrence, treatment (txt) costs, & quality-adjusted survival over a lifetime horizon. Patients transitioned between 3 health states: free of GIST recurrence, GIST recurrence, & death. Monthly recurrence & mortality rates for 3 yr & 1 yr imatinib were derived from SSGXVIII/AIO clinical trial. The 5 yr recurrence rate observed in the trial was extrapolated for the remaining duration of the model horizon. First recurrence after active txt was treated with imatinib 400 mg daily and recurrence during active txt was treated with 800mg daily. For subsequent disease progression, patients were treated with imatinib 800mg, sunitinib or best supportive care. After 5 years, txt specific mortality rate was applied for patients with recurrence. Costs & utilities were derived from published literature. Expected costs & quality-adjusted life years (QALYs) were estimated for each txt strategy. Costs & QALYs were discounted at 5% per yr. Extensive sensitivity analyses were conducted.

Results

Patients on 3 yrs of imatinib had higher QALYs (7.70 vs 6.54) vs. 1yr of imatinib. Total lifetime cost per patient was $182,000 with 3 yrs vs. $134,500 for 1 yr of imatinib therapy. Incremental cost effectiveness ratio of 3 yrs of imatinib vs 1 yr of imatinib was $40,877/QALY. Model results were sensitive to rate of GIST recurrence beyond 5 yrs. At a threshold of $100,000 or $50,000/QALY, 3yr imatinib therapy was cost-effective in 100% of simulations vs. 1 yr of imatinib.

Conclusions

Model results suggest that treating patients with 3 yrs of imatinib is cost-effective vs. 1 yr of imatinib below the commonly used threshold in Canada. Both clinical & economic results suggest treating surgically resected GIST patients with 3 yrs of imatinib would result in improved quality-adjusted & overall survival.

Disclosure

A. Parthan: Study was sponsored by Novartis and I have consulting relationship with Novartis.

M. Sanon: The study was sponsored by Novartis and I had consultancy relationship with Novartis at the time of the study.

J. Coombs: Employed at Novartis and holds Stock for Novartis.

K. El Ouagari: employed at Novartis and owns stocks for Novartis