Purpose: To explore if orbital fat-to-muscle ratio (FMR) is predictive of whether surgical decompression or teprotumumab leads to greater proptosis reduction in thyroid eye disease (TED).
Methods: A single-center retrospective cohort study comparing surgical decompression with teprotumumab according to FMR. All TED patients completing an 8-dose course of teprotumumab between January 2020 and September 2022 and all patients undergoing bony orbital decompression from January 2017 to December 2019 were included. Subjects were excluded if they were <18 years, received both surgical decompression and teprotumumab, or lacked orbital imaging. The primary exposure variable was teprotumumab or surgical decompression. The secondary exposure variable was baseline FMR. The primary outcome measure was change in proptosis (mm).
Results: Thirty-eight patients, mean age 53.5 years (±11.4), were included in the teprotumumab group and 160 patients, mean age 48 years (±11.1), in the surgical group. Average proptosis reduction after teprotumumab and surgical decompression was 3 mm (±1.44) and 5 mm (±1.75), respectively. The FMR was stratified at the median of 1.80. In subjects with FMR < 1.80, teprotumumab showed equivalent proptosis reduction compared to surgical decompression, -0.33 mm (SE 1.32) p = .802. In subjects with FMR ≥ 1.80, surgical decompression led to significantly more proptosis reduction than teprotumumab, 3.01 mm (SE 0.54), p < .001.
Conclusions: Baseline FMR can be used to counsel patients as to proptosis reduction with teprotumumab versus surgery. Subjects with low FMR obtain comparable proptosis reduction with teprotumumab or surgery, whereas high FMR is associated with more significant proptosis reduction following surgery over teprotumumab.
Keywords: Thyroid eye disease; orbital decompression; proptosis; teprotumumab; thyroid orbitopathyl.