Predicting outcome of treatment with radiotherapy in endocrine ophthalmopathy

Objective. To evaluate if the concentration of C-reactive protein and the level of antibodies to thyrotropin receptors might predict the outcome of retrobulbar irradiation in patients with endocrine ophthalmopathy.
Material and methods. Patients with moderate endocrine ophthalmopathy received orbital radiotherapy. The overall severity of endocrine ophthalmopathy was assessed using the total eye score based on the NOSPECS classification before the treatment and 6 months later. Treatment outcome was evaluated using major and minor criteria recommended by L. Bartalena 6 months after the treatment. Patients who improved in at least one major or in two or more minor criteria were considered responders. Patients in whom no changes occurred or who responded in only one minor criterion or eye status worsened were classified as nonresponders. The active disease was considered present in a patient who responded successfully to retrobulbar irradiation, and the inactive one when a patient did not respond.
Results. The level of antibodies to thyrotropin receptors in responders was 24.0 IU/L (range 2.0–405.0 IU/L) and in nonresponders 23.0 IU/L (range 2.0–405.0 IU/L); P=0.72. C-reactive protein levels in responders and nonresponders were 0.1 mg/L (range 0.1–3.1 mg/L) and 0.1 mg/L (range 0.1–1.5 mg/L), respectively; P=0.92. Although responders and nonresponders differed by proptosis, the severity of endocrine ophthalmopathy, and clinical activity score, but according to the binary logistic regression model, only the clinical activity score could give additional information on the prediction of the treatment outcome. If clinical activity score increased by 1, odds ratio for successful treatment outcome increased 2.4 times.
Conclusions. 1) At the baseline of radiotherapy, the level of antibodies to thyrotropin receptors and concentration of C-reactive protein in responders did not differ from nonresponders; 2) Responders did not differ from nonresponders to radiotherapy by age, gender, duration of endocrine ophthalmopathy and thyroid disease; 3) The pretreatment clinical activity score, total eye score, proptosis of the responders were higher.