Orbital radiotherapy for proptosis in patients with Graves’ ophthalmopathy

Background: Graves’ ophthalmopathy (GO) is an autoimmune disease of the retro-ocular tissues. The pathognomonic manifestations progressively develop from the intense recruitment of circulatory and local-infiltrating orbital immune cells followed by orbital fibroblast activation. Immunomodulatory therapy or orbital radiotherapy (ORT) is generally indicated in active GO. We evaluated the efficacy of low-dose ORT for proptosis in patients with GO. Methods: This retrospective study included patients with moderate to severe GO and proptosis who received bilateral ORT (10 fractions of 1 Gy over 2–3 weeks). The correlation between the decline of proptosis and low-dose ORT was systematically analyzed. Results: Of the 23 patients analyzed, the overall regression and nonprogression rates of proptosis were respectively 30% and 90% at 6 months, 45% and 85% at 1 year, and 56% and 89% at 2 years after low-dose ORT. The patients with ≤6 months of GO symptoms, a smoking habit, a euthyroid state, and female sex experienced a more favorable treatment response. The presence of extraocular muscle enlargement on computed tomography within 6 months of GO presentation was associated with a superior response. No side effects were observed. Conclusions: ORT alone at 10 Gy in 10 fractions is safe and effective for proptosis in patients with GO. This low fractional dose (1 Gy per fraction) may have achieved not only fewer side effects but also possibly more immunomodulatory effects compared with the results of studies using a dose of 1.8–2.0 Gy per fraction. Low-dose ORT likely produces the best outcomes when administered within 6 months of proptosis presentation, thus necessitating early referral to an ophthalmologist and radiation oncologist.