Clinical efficacy of radioactive iodine therapy in multifocal papillary thyroid microcarcinoma: a tertiary center experience.

[PURPOSE] In recent years, the increased incidence of differentiated thyroid cancers has largely been attributed to microcarcinomas. The aim of this study was to evaluate the impact of adjuvant radioactive iodine (RAI) therapy on recurrence in patients with multifocal papillary thyroid carcinoma (PTC) ≤ 1 cm.

[METHODS] A total of 74 patients who were >18 years of age and diagnosed with multifocal PTC ≤ 1 cm at a tertiary referral center between July 2015 and December 2023 were retrospectively evaluated.

[RESULTS] Of the 74 patients, 78.4% were female and 21.6% were male. The mean patient age was 45.6 ± 12.6 years, mean follow-up duration was 29.1 ± 22.8 months. Twenty two patients (29.7%) did not receive RAI [RAI (-)], whereas 52 patients (70.3%) received [RAI (+)]. Recurrence was observed in 6.7% (5/74) of patients. Four of the five recurrences occurred in patients initially managed without RAI. The recurrence rate was significantly higher in the RAI (-) group (18.2%, n = 4) compared to the RAI (+) group (1.9%, n = 1) (p = 0.011). Patients without recurrence had a mean age of 46.8 ± 12.0 years, whereas those with recurrence had a mean age of 28.6 ± 8.7 years. The mean age of patients with recurrence was significantly lower (p < 0.01).

[CONCLUSION] RAI ablation appears to improve disease-free survival in multifocal PTC ≤ 1 cm. These findings suggest that RAI therapy decisions in multifocal PTC ≤ 1 cm should be individualized based on tumor variant, invasion characteristics, and patient age.