The main DOX metabolic product, DOL, was found in much lower concentrations than DOX in the blood. These low levels of DOL made it difficult to quantify band intensity on the TLC plate and contributed to an increase in error with the HLPC-derived values. Although not as reliable as the DOX measurements, these DOL measurements do give an indication of the level of DOX metabolism that is occurring in each patient and may provide useful information to the physicians looking to individualize the DOX dose for each patient.