[Chronological patterns of lacrimal drainage obstruction following radioactive iodine therapy for differentiated thyroid cancer].

Abstract

Radioactive iodine (I-131) therapy for differentiated thyroid cancer is associated with a risk of delayed complications affecting radiosensitive organs. One such complication is secondary obstruction of the lacrimal drainage system caused by accumulation of I-131 in the wall of the nasolacrimal duct, leading to chronic inflammation and fibrosis. However, the precise chronological pattern of this pathology's onset remains undefined.

Purpose: This study investigated the chronological patterns of lacrimal drainage obstruction following radioactive iodine therapy.

Material and methods: This retrospective survey involved 375 patients who underwent a single course of radioactive iodine therapy between 2021 and 2025. The patients were stratified into five groups according to the time interval between therapy and survey: ≤6; 7-12; 13-24; 25-36; and 37-51 months. Obstruction was defined as epiphora graded 3-4 on the Munk scale. Statistical analysis included Pearson's χ² test, Fisher's exact test, and linear trend analysis (p<0.05 was considered significant).

Results: No cases of lacrimal drainage obstruction were identified within the first 6 months after therapy, then the frequency of complications increased progressively: 6.3% (7-12 months), 11.3% (13-24 months), and 13.6% (25-36 months), followed by a decrease to 7.5% (37-51 months). The association with time since radioactive iodine therapy was statistically significant (p=0.014; p=0.002). After 6 months, the association lost statistical significance (p=0.455), indicating risk stabilization. The probability of obstruction was significantly higher in men (χ²=5.637; p=0.018). The administered activity of I-131 had no statistically significant impact.

Conclusion: Lacrimal drainage obstruction is a delayed complication of radioactive iodine therapy for differentiated thyroid cancer, with a peak incidence at 25-36 months after treatment. The critical screening period is 6-51 months post-therapy. Early diagnosis and timely referral to an ophthalmologist improve the effectiveness of minimally invasive interventions.