Positron emission tomography (PET) is now regularly used in the diagnosis and staging of cancer. These uses and its ability to monitor treatment response would be aided by the development of imaging agents that can be used to measure tissue and tumor proliferation. We have developed and tested [F-18]FLT (3'-deoxy-3'-fluorothymidine); it is resistant to degradation, is retained in proliferating tissues by the action of thymidine kinase 1 (TK), and produces high-contrast images of normal marrow and tumors in canine and human subjects.

This investigation confirms that FDG PET is the best predictor of viable residual tumor in postchemotherapy seminoma residuals and should be used as a standard tool for clinical decision making in this patient group.

Abstinent alcoholic patients displayed an increase in mu-opiate receptors in the ventral striatum, including the nucleus accumbens, which correlated with the severity of alcohol craving. These findings point to a neuronal correlate of alcohol urges.

The aim of this study was to evaluate the use of [(18)F]fluorothymidine (FLT) as a positron emission tomography (PET) tracer for the diagnosis of breast cancer. To this end, 12 patients with 14 primary breast cancer lesions (T2-T4) were studied by FLT-PET. For comparison, [(18)F]fluorodeoxyglucose (FDG) PET scans were performed in six patients. Thirteen of the 14 primary tumours demonstrated focally increased FLT uptake (SUV(mean)=3.4+/-1.1). Seven out of eight patients with histologically proven axillary lymph node metastases showed focally increased FLT uptake in the corresponding areas (SUV(mean)=2.4+/-1.2). The lowest SUV (mean =0.7) was observed in one of two inflammatory cancers. The contrast between primary tumours or metastases and surrounding tissue was high in most cases. In direct comparison to FDG-PET, the SUVs of primary tumours (5/6) and axillary lymph node metastases (3/4) were lower in FLT-PET (SUV(FLT): 3.2 vs SUV(FDG): 4.7 in primary tumours and SUV(FLT): 2.9 vs SUV(FDG): 4.6 in lymph node metastases). Since FLT uptake in surrounding breast tissue was also lower, tumour contrast was comparable to that with FDG. It is of note that normal FLT uptake was very low in the mediastinum, resulting in a higher tumour-to-mediastinum ratio as compared to FDG ( P=0.03). FLT-PET is suitable for the diagnosis of primary breast cancer and locoregional metastases. High image contrast may facilitate the detection of small foci, especially in the mediastinum.