P528 Effectiveness, Safety and Incremental Costs of Proactive Therapeutic Drug Monitoring of Infliximab in a Prospective Cohort of Inflammatory Bowel Disease Patients
Zelinkova, Z.(1)*;Podmanicky, D.(2);Kadleckova, B.(1);
(1)Nemocnica Bory - Penta Hospitals, Department of Gastroenterology, Bratislava, Slovakia;(2)Nemocnica Bory - Penta Hospitals, Department of Surgery, Bratislava, Slovakia;
Background
The use of infliximab (IFX) is limited by low treatment persistence. Proactive therapeutic drug monitoring (pTDM) has been shown to increase the treatment persistence in inflammatory bowel disease (IBD) patients but the real-life data evaluating effectiveness, safety and costs of this approach are scarce. Therefore, the aim of this study was to assess survival on treatment, safety and costs of pTDM of IFX in the treatment of IBD.
Methods
IBD patients who started IFX in a referral centre using pTDM between January 2018 and March 2021 were included. The main outcomes were treatment persistence, adverse events and incremental costs of pTDM.
IFX trough levels were assessed in the week 14 and subsequently every six months by commercially available ELISA kit (Ridascreen R-Biopharm) and with the cut-off level of 3μg/ml .
Costs related to the measurements of levels and the costs of intensified treatment were calculated. The costs of pTDM were compared with costs of a modelled cohort using reactive TDM (rTDM) based on the data from the same cohort. The model used arbitrarily determined intensification regimen to 5mg/kg of IFX every 4 weeks in case of pharmacokinetically determined clinical or endoscopic loss of response. The calculation was performed for the first year of treatment.
Results
Overall, 99 patients with IBD were included (58 men – 59%; mean age 39,96 years, minimum-maximum, 20-73 years; 64% patients with Crohn´s disease; mean disease duration 103 months, minimum – maximum, 8-402 months).
The treatment was intensified in 57 patients (58%). Overall treatment survival using pTDM was 87% at 6 months, 77% at one year, 66% at two years and 60% at both, the third and fourth year of treatment. There were no differences between patients on conventional regimen vs. intensified regimen with regards to adverse events.
The costs related to pTDM in this cohort of 99 patients were € 90 306,56 while the costs of the modelled cohort using rTDM were € 24 846,30. The overall incremental costs were thus € 65 460,26 with mean costs per patient for the first year of treatment of € 661,21.
Conclusion
Proactive TDM of IFX results in a steady 60% treatment persistence beyond the second year of treatment with no impact on the safety. In the context of this solid treatment persistence, the incremental costs related to proactive TDM seem negligible when considering the costs of alternative biologicals used in case of loss of response to IFX.