Randomized controlled trials are still missing in which RRIA has proven its worth as a safe and very effective treatment that results in an improved life expectancy and a reduced recurrence rate. Many observational studies lack sufficiently high evidence. Evidence grade is rated mainly on "expert level", based on non-randomized retrospective observation studies. Although RRIA in Europe is established as adjuvant standard treatment for all patients with DTC, except those with stage T1a, it remains to be shown throughout if it is beneficial for low risk and medium risk patients without metastases (M0), also known as stage I patients according to UICC/AJCC classification, accounting for 40-90% of all patients.