The potential of iodine for improving breast cancer diagnosis and treatment

Abstract

Early detection through modalities such as mammography remains pivotal in the fight against breast cancer. The detectability of breast cancer through mammography is rooted in the differential X-ray attenuation properties of cancerous and normal breast tissue. An unexplored component of the X-ray contrast between fibrous breast tissue and similarly composed tumor tissue is the presence of naturally localized iodine in the cancer but not healthy breast tissue. It is hypothesized that differing amounts of iodine are present in tumor versus normal breast tissue that leads to more easily detectable cancer due to an increased Z value of the tumor tissue relative to the healthy tissue, which results in enhanced differences in X-ray attenuation properties between the two tissues and thus greater radiographic contrast. The hypothesis is supported by experimental observations explaining how iodine could localize in the tumor tissue but not surrounding healthy tissue. Breast cancer cells express the sodium–iodide symporter (NIS), an ion pump which sequesters iodine in tumor cells. Healthy non-lactating breast tissue, in contrast, does not express NIS. Further evidence for the differential expression of NIS resulting in X-ray contrast enhancement in breast cancer is the established correlation between expression of insulin growth factor (IGF) and enhanced X-ray contrast, and the evidence that IGF is a promoter for NIS. Ultimately, if the expression of iodine can be shown to be a component of radiographic contrast between healthy and tumor breast tissue, this could be used to drive the development of new technology and techniques for use in the detection and treatment of breast cancer. The proof of this hypothesis could thus have a substantial impact in the fight against breast cancer.