Drug plasma monitoring has emerged as an important tool to obtain optimal levels 
of a particular drug among individual patients. Plasma monitoring of imatinib 
levels would appear to be practical in cases where there is lack of response, 
heightened toxicity, or evidence of poor adherence to therapy. However, the 
potential role of monitoring plasma drug concentrations in guiding treatment 
decisions and optimizing patient therapy has yet to be established. Currently, 
there are no clinical recommendations regarding how to incorporate imatinib drug 
plasma monitoring in patients with either chronic myeloid leukemia or 
gastrointestinal stromal tumors, indications for which imatinib is approved. 
Here, the latest research and evidence regarding imatinib drug plasma monitoring 
is discussed. Three cases are presented to illustrate the most common examples 
where monitoring imatinib plasma concentrations may help to guide treatment 
decisions. These cases include a suboptimal response to imatinib treatment, lack 
of patient adherence to imatinib, and imatinib-related toxicity. By 
understanding the potential role of monitoring plasma imatinib concentrations in 
patients with chronic myeloid leukemia or gastrointestinal stromal tumors, 
physicians can identify patients who may benefit from drug plasma monitoring and 
consider incorporating the data in order to improve patient outcomes.