NONINVASIVE MONITORING OF TUMOR METABOLISM USING FLUORODEOXYGLUCOSE AND POSITRON EMISSION TOMOGRAPHY IN COLORECTAL-CANCER LIVER METASTASES - CORRELATION WITH TUMOR RESPONSE TO FLUOROURACIL

Purpose: To investigate and measure the metabolism of colorectal cance r liver metastases using 18F-fluorodeoxyglucose positron emission tomo graphy (FDG PET), before and during the first month of chemotherapy. T he findings were compared with tumor outcome conventionally assessed u sing changes in tumor size. Patients and Methods: Patients with colore ctal cancer liver metastases were treated with fluorouracil (5FU) as a protracted venous infusion (300 mg/m(2)/d), with or without interfero n-alpha 2b for two 10-week blocks separated by a 2-week break. Before and at 1 to 2 and 4 to 5 weeks on treatment, FDG PET scans were perfor med. Patients fasted, were injected intravenously with FDG (50 to 100 MBq), and scanned using a large-area positron camera; the image data w as processed such that regions of interest could be identified. The re sults were expressed as a ratio of FDG uptake in the tumor and normal liver (T:L) or as a semiquantitative standardized uptake valve (SUV). These measures were compared with the tumor dimensions measured on a c omputed tomographic (CT) scan performed at 1 2 weeks from commencement of chemotherapy. Results: Twenty patients were studied; however, two did not have assessable liver metastases. Objective partical responses were observed in 11 of 18 patients. A total of 27 metastatic lesions were assessable. Pretreatment T:L ratios and SUVs did not correlate wi th tumor response, although response was associated with lower 1- to 5 -week (1.84 v 2.17; t = 2.667; P < .02) and 4- to 5-week (1.36 v 2.28; t = 5.02; P < .001) T:L ratios, and 4- to 5-week (3.57 v 4.95; t = 2. 492; P < .05) SUVs. Expressed as a percent of the baseline values of t he T:L ratio, responding lesions had a greater reduction in metabolism (67% v 99%; t = 7.53; P < .001). The 4- to 5-week T:L ratio was able to discriminate response from nonresponse both in ct lesion-by-lesion and overall patient response assessment (sensitivity 100%; specificity 90% and 75%, respectively). Conclusion: Positron emission tomography used to evaluate uptake of FDG in tumors yields data that correlate wi th the antitumor effect of chemotherapy in patients with liver metasta ses from colorectal cancer. (C) 1996 by American Society of Clinical O ncology.