Assessment of response to cancer therapy using fluorine-18-fluorodeoxyglucose and positron emission tomography.

In order to evaluate the usefulness of 18F-FDG PET in the assessment of therapeutic effects, FDG-PET studies were performed both before and after therapy in 26 patients with miscellaneous malignant tumors. The change in FDG uptake by therapy was compared with the change in tumor size and prognosis. All 26 lesions had a high FDG uptake before therapy. Five of seven lesions which had a relatively low FDG uptake before therapy showed no change or increase in tumor size by therapy. The decreased FDG uptake after therapy was more prominent in the partial response group than in the no change group. FDG uptake before therapy in the non-relapse group was higher than that in the relapse group. However, a decreased FDG uptake did not necessarily indicate a good prognosis. One patient with no change in tumor size and a decreased FDG uptake had no recurrence. This suggests that FDG-PET has a complementary role in the assessment of therapeutic effects.