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P317. Cost-effectiveness of top-down versus step-up strategies in patients with newly diagnosed active luminal Crohn's disease (CD)

A. Di Sabatino1, M. Marchetti2, L. Liberato3, P. Biancheri1, M. Guerci1, G.R. Corazza1

1First Department of Medicine, Fondazione IRCCS Policlinico S. Matteo, University of Pavia, Pavia, Italy; 2Internal Medicine Department, C. Massaia Hospital, Asti, Italy; 3Internal Medicine Department, Azienda Ospedaliera della Provincia di Pavia, C. Mira Hospital, Casorate Primo (PV), Italy

Background: Frontline treatment with azathioprine and infliximab in newly diagnosed CD patients (top-down strategy) proved to significantly reduce relapses and ameliorate quality of life when compared to step-up strategy (infliximab after failure of steroids and immunosuppressants) [1].

Aim: To evaluate the cost-effectiveness and cost-utility of top-down strategy compared to the step-up one.

Methods: We considered two hypothetical cohorts of patients, clinically similar to those enrolled in the trial of D'Haens et al. [1]. A Markov model has been used to represent patients' monthly transitions among different disease states. A 5-year temporal horizon has been adopted. Transition probabilities between states were estimated from the randomized trial [1]. Probabilities of flares in the third and subsequent years were based on the reported mucosal healing rates. Direct costs were estimated based on the Italian (Lombardia Region) Healthcare System. Time spent in the model was weighted for quality of life assigning quality-adjusting factors (QAF) ranging from 1 (the best) to 0 (the worst). When remaining in the same state patients accumulate life years (LYs), quality adjusted life years (QALYs) and costs. From these figures, incremental cost/effectiveness (ratio between gains in LYs and costs, ICER) and cost/utility (ratio between gains in QALYs and costs, ICUR) ratios have been calculated. A 3.5% discount factor has been used for costs as well as utilities.

Results: Baseline analysis showed that quality-adjusted life expectancy improved from 3.45 to 3.59 QALYs, that is 0.14 QALYs in favour of top-down strategy. Accordingly, top-down strategy allowed to save €252, proving to be “dominant”, i.e. both cost-saving and effective. Sensitivity analysis showed that top-down strategy would not be cost-saving: (1) if it did not reduce surgery rate by more than 47% (baseline 55%); (2) if infliximab cost more than €556 (baseline €512) per 100 mg vial; (3) if relapse rate decrease by less than 2% per year. Monte Carlo analysis showed that top-down strategy was: (1) cost-saving in 63% of the simulations (III plus IV); (2) more effective in 96% of the simulations (I plus IV); (3) dominant (i.e. both cost-saving and more effective) in 60% (IV).

Conclusions: In our analysis, top-down strategy proved to be cost-effective in naïve CD patients, and sensitivity analysis showed the result to be robust.

1. D'Haens G, et al. Lancet 2008;371:660.