Imatinib plasma levels in patients with gastrointestinal stromal tumour under routine clinical practice conditions

• Published in: Journal of oncology pharmacy practice Vol. 29; no. 7; pp. 1613 - 1618
• Main Authors: Del Rosario García, Betel, Morales Barrios, José Alberto, Jurado, Josefina Cruz, Díaz, Ruth Ramos, Viña Romero, María Micaela, Padrón, Ivette Mourani, Nazco Casariego, Gloria Julia, Nicolás, Fernando Gutiérrez
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-10-2023; Sage Publications Ltd
• Subjects: Clinical medicine; Gastrointestinal cancer; Imatinib; Metastases; Metastasis; Patients; Plasma; Plasma levels; Survival; Survival value; Toxicity; Tumors; plasma concentrations; Imatinib; pharmacokinetic monitoring; plasma levels; gastrointestinal stromal tumours
• ISSN: 1078-1552; 1477-092X
• DOI: 10.1177/10781552221143788

Objectives
Imatinib is the first therapeutic option for the treatment of unresectable or metastatic gastrointestinal stromal tumours. Previous studies have shown an improvement in patient survival rates following the use of imatinib. Nevertheless, adequate plasma concentrations of imatinib are necessary to achieve such improvement in survival and limit the toxicity of the drug. This study aims to analyse the influence of imatinib plasma concentrations on efficacy and safety in the treatment of gastrointestinal stromal tumour.
Materials and methods
This descriptive, multicentre study analysed plasma levels of imatinib in patients diagnosed with gastrointestinal stromal tumour in the period 2019–2020. An optimal therapeutic range of 750–1500 ng/mL was established for the patient stratification based on their minimum plasma concentrations measured at the steady state.
Results
This study included 11 patients with metastatic disease in total, among whom only 54.5% (n  =  6) had a minimum plasma concentrations measured at the steady state value within the therapeutic range. A median progression-free survival of 7.0 months was recorded for those patients with minimum plasma concentrations measured at the steady state < 750 ng/mL, while that median progression-free survival value remained unachieved for the group with minimum plasma concentrations measured at the steady state > 750 ng/mL (p  =  0.005). The toxicity rate was 25% and 14.3% for patients with minimum plasma concentrations measured at the steady state > 1500 ng/mL and minimum plasma concentrations measured at the steady state ≤1500 ng/mL, respectively (p  =  0.66).
Conclusions
The present study aims to describe the correlation between the toxicity and effectiveness of imatinib as a function of minimum plasma concentrations measured at the steady state under routine clinical practice conditions. The results described here show the usefulness of imatinib plasma concentrations monitoring as part of the standard daily routine in our hospitals.