Thyroid Cancer Therapy with 131I: A Comprehensive Review

1281 Objectives • Review of thyroid cancer subtypes. • Review the three major 131I treatment categories: remnant ablation, adjuvant therapy, and cancer treatment (radioiodine therapy) as defined by the American Thyroid Association (ATA), National Comprehensive Cancer Network (NCCN) and Society of Nuclear Medicine and Molecular Imaging (SNMMI) guidelines. • Review the diagnostic approach of patients with iodine-refractory thyroid cancer. • To present and review interesting cases of thyroid cancer patients. Methods First we will review the different thyroid cancer subtypes. A review of the guidelines for treatment with 131I treatment as recommended by the ATA, NCCN and SNMMI will follow. Patient selection criteria and dose recommendations will be discussed. The recommended approach to iodine refractory thyroid cancer patients will be reviewed. Finally, we will summarize with a review of interesting cases showing correlative imaging analysis. Results The incidence of thyroid cancer has increased over the years. The American Cancer Society estimated that approximately 62,450 new thyroid cancer cases would be diagnosed in 2015 (47,230 in women, and 15,220 in men). Death rate remains stable and differentiated papillary thyroid carcinoma continues to be the most common subtype with excellent prognosis for early stage newly diagnosed patients. The efficacy of surgery with adjunct radioactive iodine treatment has been proven throughout many years of successful practice. However, according to the ATA and NCCN, not all patients require treatment with Iodine 131I. Patients that will benefit from treatment are divided into three major categories: 1) Remnant ablation: Treatment of low risk patients after successful thyroidectomy with minimal remnant of thyroid tissue. 2) Adjunctive therapy: Patients with high risk for recurrence after thyroidectomy with no evidence of disease. 3) Cancer treatment (known as radioiodine therapy): Patients with known recurrence or residual disease after thyroidectomy. Despite a high success rate, some patients fail to respond to radioablation treatment and their cancer is considered to be “Iodine-refractory”. 18F-FDG PET/CT has demonstrated utility in the diagnosis and localization of non-iodine avid disease. Through an interactive presentation of different cased-based clinical scenarios, we will discuss the recommended protocols; importance of pre and post stimulation thyroglobulin levels, thyroglobulin antibodies, and recommended dose determination protocols. Conclusions The reviewer will be able to recognize and master the most important points in the current guidelines for thyroid cancer treatment including patient selection and dose determination as recommended by the ATA, NCCN and SNMMI. The reviewer will also learn to identify the selected group of patients considered to have iodine-refractory thyroid cancer and the emerging options for imaging, follow up and possible adjunctive treatment. RESEARCH SUPPORT: 1. Worden F. Treatment strategies for radioactive iodine-refractory differentiated thyroid cancer. Therapeutic Advances in Medical Oncology. 2014;6(6):267-279. doi:10.1177/1758834014548188. 2. Cooper, Doherty, et al., Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid 19(11): 1167-1214, 2009.