Iodine-labeled tamoxifen uptake in primary human breast carcinoma.

UNLABELLED Assessing tumor uptake and retention of (123)I-labeled tamoxifen (TX) could increase our understanding of TX's action and the mechanisms involved in resistance to the drug. METHODS Nine untreated primary breast carcinoma patients underwent whole-body planar and tomographic (SPECT) imaging 30 min and 4-5 h after injection of 185 MBq (123)I-TX. Tumor-to-normal tissue uptake ratios (T/N) derived from SPECT images were related to estrogen receptor (ER) and progesterone receptor (PR) status. RESULTS In 4 of 9 patients, all of whom were ER+/PR+, (123)I-TX tumor uptake was clearly depicted. In 2 of them, involved axillary lymph nodes were also visualized. T/N consistently increased over time. All ER+/PR- and ER-/PR- tumors as well as 2 ER+/PR+ tumors were (123)I-TX-. CONCLUSION These preliminary findings suggest that (123)I-TX is preferentially taken up in alpha-ER+/PR+ breast tumors known to be more likely to respond to endocrine treatment.