Identification of breast cancer by differences in urinary iodine

2150 Introduction: Iodine is involved metabolically in normal, nursing, and neoplastic breast tissues. Our objective was to evaluate differences in urinary iodine levels in women with benign and malignant breast changes. Methods: Ninety-eight women with a median age of 47 years (range 15-87) presenting with benign or malignant breast diagnoses to the university breast center participated in this study. Women with a history of hyper/ hypothyroidism were excluded. Urine specimens were collected following informed consent. Urine was quantified by chromatography/anion exchange resin. Values are reported as micrograms (mcg) iodine or milligrams (mg) bromide per liter by ion selective electrode assay. A t-test was used to compare means. Results: Our final cohort included 20 women with cancer (DCIS =6; invasive cancer=14), 20 women who were smokers and 42 who were post menopausal. A significant difference in iodine excretion between women with cancer (105 mcg/l) versus non-cancer (141 mcg/l, p Trends seen were: 1) Higher excretion (26%) in postmenopausal versus premenopausal women (152 mcg/l vs. 121 mcg, p=NS). 2) Smokers had lower (23%) iodine excretion (109mcg/l vs. 141mcg/l, p=NS). 3) Lower iodine excretion in women with cancer, regardless of menopausal status. In order to control for halide effect, urinary bromide level was determined in a subset of these women (n=47). Urinary bromide levels trended towards higher excretion by 64% in women without cancer (18.5 mg/l vs. 11.3 mg/l, p=NS), in premenopausal women by 36% (20.5mg/l vs. 15.1mg/l, p=NS), and smokers by 35% (22.7mg/l vs. 16.8mg/l, p=NS). Discussion: These preliminary results are the first to show a significant decrease in iodine excretion in women with malignant breast diseases. Basic studies have shown a significantly lower iodine availability in breast tissue harboring malignancy. These data indicate that iodine plays a role in breast cell differentiation. These provocative findings imply potential diagnostic and therapeutic capabilities in the iodine pathway.