Long-term scintigraphic and clinical follow up in patients with differentiated thyroid cancer and iodine avid bone metastases Omnia Mohamed Talaata, Ismail Mohamed Alib, Sherif Maher Abolyazidc, Bader Abdelmaksoudd and Ibrahim Mansour Nasrd Aim The aim of this study was to evaluate the long-term overall therapy outcomes and clinicopathological risk factors in patients with differentiated thyroid cancer (DTC) and iodine avid bone metastases. Methods Our study included 93 patients [female to male ratio (2:1)]. All patients were subjected to clinical examination, laboratory assessment, I-131 whole body 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) and stable disease (SD)], and progressive disease (PD). Results Fifty-four patients had follicular carcinoma and 39 with papillary type. Isolated bone metastases, bone and lung metastases, and multi-organ metastases were found in 45, 34, and 14 patients, respectively. The overall CR, PR, SD, and PD were found in 8.6%, 28%, 46.2%, and 17.2% patients, respectively. Adjunctive radiotherapy resulted in more CR, IR, and low PD rates compared to RAI-131 therapy (9.0%, 78.3%, 12.7% vs. 7.9%, 56.8%, and 23.7%, respectively) (P = 0.03). The overall survival rate was 88.2% and median follow-up period was 123 months. Female patients, papillary carcinoma, and single focal lesion had better overall response rate. Males, extrathyroidal extension, vascular invasion, and lymph nodes metastases had increased PD and decreased global response rates. Conclusion Despite of low CR rate (8.6%), most patients with DTC and iodine avid bone metastases had SD (46.2%) and long lived (88.2%). Adjunctive radiotherapy reduced PD and improved outcome. Males, extra thyroid extension and vascular invasion were bad prognostic factors.