Poster Presentation The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2017

Clinical audit in the use of low versus high dose radioactive iodine in thyroid cancer: a local viewpoint (#206)

Aditi Nevgi 1 , Michael Mond 1 , Jennifer Wong 1
  1. Endocrinology, Monash Health, Clayton, Victoria, Australia


Recent changes to recommendations regarding radioactive-iodine (RAI) therapy for thyroid cancer represent a significant shift in clinical practice. Studies indicate that low-dose RAI is as effective as high-dose for remnant ablation[1,2]. We reviewed the practice at our institution and its consistency with guidelines, and the factors influencing clinician decision-making around RAI dose.



A retrospective audit was conducted of adult patients in our institution. Participants had thyroid cancer (any variant), with initial RAI ablation between 29/08/2014–21/04/2017. Exclusion criteria included patients with irretrievable histology, or with metastatic disease without primary cancer in the thyroid. Patients received either low-dose (≤60mCi) or high-dose (>60mCi) RAI; most dose recommendations were made in a specialised clinic or by multidisciplinary consensus.

Chi-squared tests and logistical regression were used, with a significance cut-off of p=0.01.



112 patients were eligible. 35% received low-dose RAI; 65% received high-dose. High dose was associated with increasing MACIS score. Every 1 increase in MACIS increased the likelihood of receiving high-dose RAI 1.68 times (Chi2=13.49 with 1df; p=<0.001).  American Thyroid Association (ATA) score was also correlated (OR=4.68, Chi2=11.46 with 1df; p=0.001).

RAI dose was not correlated with age above/below 45 (OR=2.33, Chi2=3.99 with 1df; p=0.046), histology (OR=1.6, Chi2=0.57 with 1df; p=0.45), or males/females (Chi2=1.81 with 1df; p=0.18). There was no significant difference in RAI dose received for stages 1 versus stages 2/3 (OR=1.37, Chi2=1.50 with 1df, p=0.22).



High-dose RAI appropriately correlated with ATA score, and MACIS (MACIS scores ≥7 are considered high-risk for mortality). Interestingly, other factors associated with mortality rate, namely age ≥45 and stage, were not associated with high-dose, however the study may be underpowered for these outcomes.

Overall, substantial patients received high-dose RAI. More judicious use of high-dose RAI may be appropriate given the higher rate of side-effects[2] and small risk of secondary malignancy.

  1. 1. Schlumberger, M, Catargi, B, et al. Strategies of Radioiodine Ablation in Patients with Low-Risk Thyroid Cancer. N Engl J Med, 2012. 336; 1663-1673.
  2. 2. Mallick, U, Harmer, C, et al. Ablation with low-dose radioiodine and thyrotropin alfa in thyroid cancer. N Engl J Med, 2012. 336; 1674-1685.