Imaging Head and Neck Cancer Using Radioisotopes: A Review

The accumulation of radioactive iodine in metastatic thyroid cancer was reported in 19421, and iodine isotope (1311) thyroid scanning was introduced into clinical practice 9 years later'', The discovery that the isotope of technetium (99mTc) pertechnate (TcO~ was trapped by the thyroid gland" led to its routine use in imaging'. Together with 1231 and 1311, it is the current agent of choice to diagnose and treat differentiated thyroid malignancy", Other radiopharmaceuticals may be used to image both thyroid cancer and other head and neck malignancies, and with the wider availability of radioisotopes, together with improved technology, there has been a renewed interest in imaging head and neck cancers. This paper reviews the clinical use of radiopharmaceuticals currently available to image head and neck cancer. Tumour localizing radiopharmaceuticals for imaging head and neck cancer may be divided into specific and non-specific agents. Tumour-specific agents localize only within one specific tumour, or follow one specific metabolic pathway and include 1311 for differentiated thyroid cancer, 99mTc(V) dimercaptosuccinic acid for medullary thyroid cancer, and indium isotope (lIIln) monoclonal antibodies for squamous cell carcinoma (SCC). Tumour-nonspecific agents localize not only in a number of histologically different malignant tumours, but also in benign tumours and inflammatory lesions. Examples within the head and neck include gallium (67Ga)..citrate for lymphoma, and thallium (201T1)-chloride for differentiated thyroid cancer.