The solitary use of the size of the tumor during evaluation for response to chemotherapy has some pitfalls and limitations, especially for specific tumors such as gastrointestinal stromal tumor (GIST).
The Choi response criteria for GIST proposed that tumor attenuation could provide an additional measure of response to imatinib therapy.
- Disappearance of all target lesions
- ≥10% decrease tumor size at computed tomography (CT);
- or ≥15% decrease in tumor attenuation at computed tomography (CT);
- no new lesions
- ≥10% increase in sum of longest diameters (SLD) of lesions;
- does not meet the criteria for partial response by virtue of tumor attenuation;
- new intratumoral nodules
- or an increase in the size of the existing intratumoral nodules
- none of the above