Radiotherapy in the management of thyroid orbitopathy. Computed tomography and clinical outcomes

OBJECTIVE: We investigated the long-term outcome of patients with thyroid orbitopathy treated with orbital radiotherapy using quantitative clinical measurements and orbital computed tomographic morphometric changes. DESIGN: Patients who had undergone orbital radiotherapy for thyroid orbitopathy at least 1 year previously were retrospectively recalled for follow-up examination and computed tomography. Controls were patients with similar disease activity but who had not undergone radiotherapy. SETTING: Subspecialty clinic in a university teaching hospital. PATIENTS: Twenty-one patients (42 orbits) who underwent radiotherapy and six clinically comparable patients who had not undergone radiotherapy (12 orbits). INTERVENTION: Standardized, super-voltage, orbital radiotherapy. MEASUREMENTS: Five clinical indexes of orbitopathy and six computed tomographic indexes were examined for interval changes. RESULTS: The orbital computed tomographic muscle-diameter index enlargement ratio did not change in either group (radiotherapy group, 1.54 to 1.51, not significant; nonradiotherapy group, 1.37 to 1.36, not significant). The mean (+/- SEM) number of muscles with low-density areas increased in both groups (radiotherapy group, 1.1 [+/- 1.9] muscles per orbit; P < .001). Soft-tissue signs improved significantly with lesser improvements in extraocular muscle function in both groups. Proptosis, visual acuity, and intraocular pressure rise on upgaze did not improve significantly in either group. CONCLUSIONS: No changes in muscle size measured with computed tomography were found in either patients undergoing radiotherapy or patients not undergoing radiotherapy after long-term follow-up. Clinical indexes of thyroid orbitopathy, especially soft-tissue signs, improved on follow-up, but this was not influenced by the method of treatment.