Patterns of radioiodine use for differentiated thyroid carcinoma in Brazil: insights and a call for action from a 20-year database.

Objective: This study aimed to explore the patterns of radioactive iodine (RAI) use for differentiated thyroid cancer (DTC) in Brazil over the past 20 years.
Methods: A retrospective analysis of the DTC-related RAI prescriptions, from 2000 to 2018, retrieved from the Department of Informatics of the Unified Health System (Datasus) and National Supplementary Health Agency (ANS) database was performed. RAI activities prescriptions were re-classified as low (30-50 mCi), intermediate (100 mCi), or high activities (>100 mCi).
Results: The number of DTC-related RAI prescriptions increased from 0.45 to 2.28/100,000 inhabitants from 2000 to 2015, declining onwards, closing 2018 at 1.87/100,000. In 2018, population-adjusted RAI prescriptions by state ranged from 0.07 to 4.74/100,000 inhabitants. Regarding RAI activities, in the 2000 to 2008 period, the proportion of high-activities among all RAI prescriptions increased from 51.2% to 74.1%. From 2009 onwards, there was a progressive reduction in high-activity prescriptions in the country, closing 2018 at 50.1%. In 2018, the practice of requesting high-activities varied from 16% to 82% between Brazilian states. Interestingly, variability of RAI use do not seem to be related to RAI referral center volume nor state socio-economic indicators.
Conclusion: In recent years, there has been a trend towards the lower prescription of RAI, and a reduction of high-activity RAI prescriptions for DTC in Brazil. Also, significative inter-state and inter-institutional variability on RAI use was documented. These results suggest that actions to advance DTC healthcare quality surveillance should be prioritized.