18F-labeled fluorouracil positron emission tomography and the prognoses of colorectal carcinoma patients with metastases to the liver treated with 5-fluorouracil.

Background: Although many factors have been investigated in connection with the prognoses of colorectal carcinoma patients with metastases to the liver, a means for evaluating response and prognosis prior to the administration of standard chemotherapy has not been available. Positron emission tomography (PET) is a noninvasive means of measuring the distribution of radiolabeled cytostatic agents in tumor regions.

Methods: Prior to the administration of 5-fluorouracil chemotherapy, the authors examined 14 colorectal carcinoma patients with unresectable liver metastases using a single PET scan and 18F-labeled fluorouracil (18F-FU). Clinical response and survival time were correlated with 18F-FU uptake values (SUV) measured in liver metastases 120 minutes after tracer infusion.

Results: Trapping of 18F-FU varied even among different metastases in the same patient. The range of SUV was 0.9-4.3 (mean, 2.20). Four patients with SUV exceeding 2.8 had stable disease for longer than 12 months and survived longer than 21 months. Three patients with SUV less than 1.2 had progressive disease and survived less than 12 months. The 6 patients with partial remission or stable disease had a mean SUV of 2.96 and a mean survival of 31.6 months. Eight patients with progressive disease had a mean SUV of 1.59 and a mean survival of 14.5 months (Student's t-test, P < 0.012). In scatterplot analysis, there was a statistically significant correlation between SUV and survival time.

Conclusions: Patients with high 18F-FU uptake values are more likely to achieve at least stabilization of disease with planned chemotherapy. 18F-FU PET may be a valuable new tool for determining, prior to 5-FU-based chemotherapy, which patients are likely to have good responses and prolonged survival.