Abstract
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Introduction: RAIR-DTC is an uncommon entity, occurring with an estimated incidence of 4-5 cases/year/million people. A 10-year survival rate of RAIR-DTC is usually less than 10% and the mean life expectancy is 3-5 years. In contrast, well differentiated thyroid cancer has a favourable prognosis with a 10 year survival rates of about 90%.
The term non-radioiodine avidity was first reported by as early as 1952. However, no explicit statement had been clearly defined about radioiodine-refractory-differentiated thyroid cancer (RAIR-DTC) until September 2010.
Radioiodine-refractory structurally evident DTC is classified in patients with appropriate TSH stimulation and iodine preparation in four basic ways: (i) the malignant/metastatic tissue does not ever concentrate RAI (no uptake outside the thyroid bed at the first therapeutic WBS), (ii) the tumor tissue loses the ability to concentrate RAI after previous evidence of RAI-avid disease (in the absence of stable iodine contamination), (iii) RAI is concentrated in some lesions but not in others; and (iv) metastatic disease progresses despite significant concentration of RAI. Additionally after receiving more than 600 mCi of RAI and patients with locally advanced or end stage disease not amenable to surgery.
Objective The purpose of this presentation is (i)To present major classifications of radioiodine refractory disease in DTC, (ii) factors to be considered before designating a patient's DTC as radioiodine refractory, (iii) potential approaches and available treatment options, (IV) Role and clinical utility of nuclear medicine imaging in identifying RAI-R disease.
Methods: Methods The patients’ charts were reviewed for information on treatment detail and laboratory findings. We selected and deidentified images of patients designated as RAIR-DTC from our institutional PACS. These images include Iodine-131/I-123 whole body planar scans including single photon emission tomographic scan (SPECT), computed tomographic scan, 18Fluorodeoxy-glucose positron emission tomography scan (18F PETCT).
Results: Educational goals Clearly define radioiodine-refractory differentiated thyroid cancer (RAIR-DTC). Present spectrum of nuclear medicine imaging findings in patients with radioiodine refractory differentiated thyroid cancer (RAIR-DTC). Identify risk factors for radioiodine refractory differentiated thyroid cancer (RAIR-DTC). Highlight alternative treatments for RAIR-DTC
Conclusions: Conclusion The understanding and recognition of the existence of RAIR-DTCs, is important for residents and nuclear medicine physicians to early identify and even predict RAI-R disease. This will help in avoiding unnecessary radioactive Iodine radiation exposure and to explore other treatment alternatives.
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