Long term Scintigraphic and clinical follow up in Patients with Differentiated Thyroid Cancer and Iodine Avid Bone Metastases Ibrahim Nasr1, Bader Abdelmaksoud1, Ismail Ali2, Sherif Maher3, Omnia Talaat4 1Oncology and Nuclear Medicine Department, Faculty of Medicine, Zagazig University, 2Radiodiagnosis Department, Faculty of Medicine, Zagazig University, 3Radiodiagnosis Department, Faculty of Medicine, , Cairo University , 4Oncology and Nuclear Medicine Department , National Cancer Institute, Cairo University, Egypt. Nuclear Medicine Communication Journal., Jan 2019 (In press) Abstract: Aim: To evaluate the long term overall therapy outcomes and clinicopathological risk factors in patients with iodine avid bone metastases from differentiated thyroid cancer. Patients and Methods: Our study included 93 patients (62 female and 31 male). All patients were subjected to clinical examination, laboratory assessment, whole body I-131 scan and neck ultrasound. Iodine avid metastases were treated with successive radioactive iodine-131 (RAI-131) doses. The overall response was defined as complete response (CR), incomplete response (IR) [partial response (PR) & stable disease (SD)] and progressive disease (PD). Results: Thirty nine patients had papillary carcinoma and 54 with follicular type. Isolated bone metastases (BM), bone & lung metastases and multiple site metastases were found in 45, 34 and 14 patients respectively. The overall CR, PR, SD and PD were achieved in 8.6%, 28%, 46.2% and 17.2% patients respectively. Female patients, papillary carcinoma and single focal lesion had better overall response rate. Male patients, extra-thyroidal extension (ETE), vascular invasion and lymph nodes metastases had decreased global response and increased PD rates. Addition of radiotherapy (Rth) exhibits more CR and IR with low PD rates compared to I-131 therapy only with significant difference (p 0.03). The median follow up period was 123 month and overall survival rate 88.2%. Conclusion: Despite low rate of complete response in patients with iodine avid bone metastases from DTC, most of them had SD state and long survival. Female patients, papillary cancer, solitary lesion have favorable outcomes. Bad prognostic factors include male sex, ETE and vascular invasion. Key Wards: Differentiated Thyroid Cancer; Iodine and overall survival