The efficacy of radiotherapy for steroid-resistant thyroid eye disease: clinical outcomes in orbital inflammation and exophthalmos.

Purpose: This study aims to evaluate the efficacy of radiotherapy (RT) in patients with steroid-resistant thyroid eye disease (TED) by assessing clinical outcomes in orbital inflammation and exophthalmos.

Materials and methods: Sixty-two patients with confirmed TED and resistance to intravenous steroid therapy were treated with RT. Most patients received intravenous methylprednisolone (500 mg weekly for 6 weeks, followed by 250 mg weekly for 6 weeks). After steroid treatment, patients underwent RT with a total dose of 20 Gy delivered in 10 fractions. Clinical parameters were assessed at five time points: initial presentation, post-intravenous steroid therapy, and 1, 6, and 12 months after RT. Inflammation was evaluated using clinical activity score (CAS). Exophthalmos was quantified through posterior scleral distance (PSD) measurements on computed tomography imaging. Statistical analysis involved repeated measures analysis of variance and Cohen's d effect size calculations.

Results: CAS showed significant reduction from baseline (mean, 3.309) to 12 months post-RT (mean, 0.187), with the largest effect size observed between baseline and 12 months (Cohen's d = 10.88). PSD showed worsening after intravenous steroid therapy but gradually improved after RT, approaching baseline values at 12 months. Disease reactivation occurred in only two patients, and three required strabismus correction surgery. Minimal adverse events were reported during follow-up.

Conclusion: RT demonstrated significant efficacy in treating steroid-resistant TED, with sustained improvements in both orbital inflammation and exophthalmos. These findings suggest RT as a viable alternative for patients unresponsive to steroid therapy, offering meaningful long-term clinical benefits with minimal adverse effects.