Assessment of Different Radioactive Iodine Ablation Strategies in Intermediate and High Risk Papillary Thyroid Cancer

Background: Papillary thyroid cancer (PTC) represents most of cases of differentiated thyroid cancers. Thyroidectomy followed by radioactive iodine (RAI) remnant ablation represent the cornerstone management of many intermediate and high-risk patients according to American Thyroid Association (ATA).
Objective: This study aimed to evaluate the outcome of different used I¹³¹ ablation doses (80, 100 and 120 mCi) in intermediate and high-risk patients in our hospital and to analyze the predictors affecting RAI failure. Besides, survival analysis was conducted as a secondary objective of the study.
Patients and Methods: This was a retrospective study conducted on 63 patients diagnosed as PTC at our hospital from January 2015 till February 2020. Our study involved only PTC pathology, mean age of 40.6 ± 13.4 years at diagnosis, and intermediate- and high-risk patients according to ATA initial risk stratification system, 2015.
Results: Among the 63 patients included in this study (17 males and 46 females), 41 were classified as intermediate-risk, while 22 were classified as high-risk based on the ATA guideline. Overall RAI ablation success, in both groups, was observed in 43/63 (68.25%) patients. Moreover, it was achieved in 31/41 (75.6%) of intermediate-risk patients and in 12/22 (54.5%) high-risk patients. Pre-ablation stimulated Tg >1ng/ml was statistically significant negative predictor of ablation failure [P-value < 0.001, odd`s ratio 61.5, 95% CI (10.8-51.5)].
Conclusion: There was no statistically significant difference between success rates of I¹³¹ doses in intermediate- and high-risk groups. However, the failure rates were more after 120 mCi due to the associated more aggressive underlying disease, especially higher-risk patients so higher RAI activities are recommended for this risk group.