Possible role of FDG-PET in the early prediction of therapy outcome in liver metastases of colorectal cancer

Nonresectable colorectal cancer metastases in the liver respond to chemothe rapy in 20-25% only. Early identification of nonresponders might allow the use of other regimens. In a limited feasibility study, it should be determi ned whether (a) a single high-dose chemotherapy application has an early ef fect on glucose-utilization, detectable and quantitatable by noninvasive po sitron emission tomography using [18F]-Fluoro-deoxyglucose (FDG-PET) and (b ) assess its value as a predictor of the final therapeutic outcome. A total of 10 patients with documented nonresectable liver metastases of a colorec tal cancer were studied by FDG-PET, prior and 72 h after a single infusion of 5-Fluorouracil and Folinic acid (5-FU/FA), Glucose utilization was quant itated by determination of standard-uptake values and correlated with final therapy outcome following completion of the anticipated therapy cycle. Pat ients were followed up for at least 6 months. All metastases responding to therapy (n = 6) exerted a statistically significant decrease of FDG uptake (-22 +/- 10%), metastases (n = 2) showing a short-term effect (duration of tumor reduction <3 months) had a slightly diminished, and progressing metas tases (n = 3) an enhanced FDG uptake (13 +/- 17%). Our preliminary data ind icate that acute changes of glucose utilization-as detected by FDG-PET-foll owing a single application of chemotherapy, seems to be indicative for the final therapeutic outcome, at least in liver metastases of colorectal cance r.