POSITRON EMISSION TOMOGRAPHY USING [F-18] FLUOROTAMOXIFEN TO EVALUATETHERAPEUTIC RESPONSES IN PATIENTS WITH BREAST-CANCER - PRELIMINARY-STUDY

Positron emission tomography (PET) was used to assess the biodistribut ion and clinical usefulness of [F-18]fluorotamoxifen (FTX) in 10 patie nts with estrogen-receptor(ER)-positive breast tumors. Ten patients wi th ER-positive breast cancer were prospectively studied, and the conse cutive PET imagings (each takes 15 or 20 min) were obtained for 60 or 80 min after the injection of 88.8-392.2 MBq (2.4-10.6 mCi) of [F-18]F TX. Twenty three suspected primary or metastatic lesions in 10 patient s were evaluated and the tumor uptakes of [F-18]FTX in nineteen tumor lesions were correlated to the response of tamoxifen therapy. Three le sions in three patients were considered to be truly negative for breas t cancer on the bases of biopsy specimens and/or clinical course. Five (71.4%) of seven patients and 16 (80.0%) of 20 lesions were interpret ed to be truly positive for breast cancer. The mean standardized uptak e value (SW) of the radiotracer in tumor was 3.0 on delayed images. Th ere was no significant correlation between the standardized uptake val ues of [F-18]FTX and the ER concentrations in primary lesions. Ninetee n tumor lesions in six patients were evaluable to compare the [F-18]FT X uptake with responses to tamoxifen therapy after the PET study. Thre e patients who had a good response to tamoxifen therapy showed positiv e lesions on PET images, whereas two of three patients who had a poor response showed negative lesions and one showed mixed results. There w as no significant difference of [F-18]FTX uptake in bone lesions betwe en good and poor responders. However, when bone lesions were excluded, [F-18]FTX uptakes in tumors with good responses were significantly hi gher than those with poor responses (mean and standard deviation of SU V: 2.46 +/- 0.62 vs 1.37 +/- 0.59, P < 0.05). PET imaging using [F-18] FTX provides useful information in predicting the effect of tamoxifen therapy in patients with ER-positive breast cancer. Further study is w arranted to confirm the clinical utility of PET using [F-18]FTX in bre ast cancer patients.