PET studies in patients with liver metastases receiving chemotherapy

While 5-fluorouracil (FU) has been in use for chemotherapy in patients with metastatic colorectal cancer for several years, little is known about its pharmacokinetics in metastases. Positron emission tomography (PET) studies were performed with 15O-water and 18F-FU to evaluate tumour perfusion and FU pharmacokinetics. The evaluation included 50 patients (78 metastases). It was possible to compare the PET results obtained prior to the first chemotherapeutic cycle with the tumour growth rate during treatment of 25 lesions. The maximum liver activity (11.3 SUV) was achieved 30 min (mean value) after the onset of 18F-FU infusion. The mean 18F-FU accumulation in metastases was one third the concentrations measured in normal liver parenchyma 120 min post-injection. No significant correlation was noted for tumour perfusion as measured by 15O-water and FU transport (20 min SUV). Furthermore, no correlation was found between tumour perfusion and FU retention (120 min SUV). Regional tracer application resulted in higher 18F-Fu retention in 59% of the metastases. Cluster analysis was used to evaluate the correlation between tumour perfusion, FU transport and FU retention in 53 liver metastases. Two clusters were noted. While a linear correlation (r = 0.61) existed in 30 metastases (cluster I) between tumour perfusion and FU transport, no correlation was observed in the second cluster (cluster II), comprising 10 of 40 metastases. Furthermore, high FU retention (>2.0 SUV) was observed in 7 out of 10 metastases in Cluster II, but only in 1 out of 30 lesions in cluster I. A high correlation was noted between the PET 18F-FU concentration measurements and the tumour growth rate during chemotherapy. Therefore, PET studies prior to FU treatment can be used to predict therapy outcome. 4 refs, 4 figs