Orbital radiotherapy with combined intravenous methylprednisolone and mycophenolate mofetil in moderate-to-severe thyroid eye disease

Purpose

To report the clinical outcomes of orbital radiotherapy (ORT) with combined intravenous methylprednisolone (IVMP) and mycophenolate mofetil (MMF) in thyroid eye disease (TED) patients with restrictive myopathy.

Design

Prospective comparative case series of patients managed at The Chinese University of Hong Kong from 2015 to 2021.

Methods

The primary outcome was the change in Gorman diplopia score at 52 weeks. Secondary outcomes were the changes in extraocular muscle motility (EOMy), area of extraocular muscle (EOM) on MRI, exophthalmos, and marginal reflex distance (MRD) 1 and MRD2 at 52 weeks.

Results

A total of 40 (29 females) TED patients, medium age 56 years, were treated with the double regimen: combined IVMP and MMF (17) or triple regimen: IVMP, MMF, and ORT (23). The triple group has a higher age (P = 0.028). Sex, smoking history, thyroid, and pre-treatment orbital status were comparable between the 2 groups. EOMy improved more after the triple regimen(P = 0.026). Nine patients from the triple group showed a significant reduction in the size of the inferior rectus (both eyes: P < 0.05), while five from the double group showed no significant reduction of any EOM on MRI. The improvement of CAS, diplopia score, exophthalmos, MRD1, and MRD2 were similar. No patient reported any severe or organ-threatening side effects from IVMP, MMF, or ORT requiring discontinuation of treatment.

Conclusion

The triple regimen demonstrates better structural and functional outcomes in TED-related restrictive myopathy. Future randomized clinical trials are warranted to clarify the adjuvant role of ORT in this specific indication of TED management.