Blood level testing, an important component of therapeutic drug monitoring (TDM), involves measuring a drug's concentration in a patient's blood and then using that information to individualize care for your patients.¹

Therapeutic drug monitoring is critical for oral oncology drugs, because oral agents are inherently more susceptible than IV agents to intra- and interpatient variability in absorption, bioavailability, and adherence.^2,3 Sub therapeutic drug concentrations have been identified as the most important concern relating to the oral administration of anticancer agents.³

Although TKI treatment has been shown to be an effective treatment for GIST, individual patient results may vary. Blood level testing may help to illuminate causes of inadequate or unexpectedly slow responses to treatment.^4,5

Studies of TKI Treatment in GIST have shown a correlation between low drug plasma levels and inadequate response to treatment.^4,5

Suboptimal plasma levels may be due to patient non-adherence, or to factors, including⁶

• Host differences in drug absorption/metabolism
• Comorbidities
• Drug-drug interactions

Establishing a baseline blood level 30 to 90 days after the initiation of therapy can provide a reference point for future measurements and may help the clinician optimize treatment when evaluating response.