Predictive factors of prognosis after radiation and steroid pulse therapy in thyroid eye disease

To identify predictive factors of prognosis after radiotherapy with concurrent steroid pulse therapy for thyroid eye disease, retrospective analyses were performed among 77 patients. Clinical activity score and magnetic resonance imaging were used to evaluate degrees of orbital inflammation. As a pre-treatment work-up, the thyroid-stimulating antibody (TSAb) level was measured. During a median follow-up of 25.0 months, the 2-year cumulative relapse-free rate (CRFR) was 80.9%. In the univariate analysis, a worse 2-year CRFR was significantly associated with the presence of optic neuropathy (P = 0.001), a higher TSAb rate (P = 0.001), and lower standard deviation (SD) of signal intensity at the extraocular muscle in T2-weighted images (P = 0.006). In the multivariate analysis, TSAb rate and SD affected the CRFR independently. When TSAb activity of 2800% was set as a cut-off at 2 years after treatment, the predictive sensitivity and specificity of relapse were 81.2% and 90.6%, respectively. With regard to SD, the respective sensitivity and specificity values were 81.2% and 82.7% when 100 was set as a cut-off. In conclusion, high TSAb and low SD were significant risk factors for cumulative relapse in orbital radiotherapy. Cut-off values of 2800% for TSAb and 100 for SD may be suitable.