Low dose orbital radiotherapy for thyroid eye disease

The use of low dose orbital radiotherapy for thyroid eye disease (TED) remains controversial. This is a review of patients with TED treated with radiotherapy in our department over the last twelve years.

Fifty-nine consecutive patients received low dose orbital radiotherapy of 20 Gray (Gy) for active TED at the Beatson Oncology Centre. Their records were retrospectively reviewed and data including duration of symptoms, clinical activity score (CAS) pre- and post-orbital radiotherapy, immunosuppression requirement, subjective assessment and range of rehabilitative surgery was collected.

Before orbital radiotherapy, all fifty-nine patients had an initial response to glucocorticoids and therefore presumed to have active phase thyroid eye disease. They received retro-orbital radiotherapy of 20 Gy in 12 fractions over 2 weeks. After treatment, only five patients remained on steroids and only one patient had CAS ≥ 3 at last follow up. Response (change in CAS) to orbital radiotherapy was statistically significant from 3.17 ± 1.75 standard deviation (SD) to 0.73 ± 0.92 SD (P < 0.001) at mean follow up of 6.5 months. There was a reduction in CAS at each subsequent follow up for all subgroups when the patients were grouped according to disease severity i.e. mild TED(CAS 1-2), moderate (CAS 3-4), severe CAS (5-7) and optic neuropathy.

We believe orbital radiotherapy has a definite role to play in the treatment of active thyroid eye disease. The majority of our patients experienced a reduction in their clinical activity scores after orbital radiotherapy and this was irrespective of the severity of thyroid eye disease.