Proptosis reduction with teprotumumab versus surgical decompression
Reviewed by Hetvi Bhatt

This study aims to explore whether fat-to-muscle ratio (FMR) can be used to determine the efficacy of teprotumumab when compared to surgical decompression. Simply put, a high FMR equates to more fat expansion and low FMR equates to more muscle expansion. Teprotumumab is a monoclonal IgG1 antibody that should in theory downregulate orbital fibroblast activation and therefore tissue expansion. This would imply it should have more of an effect on the extra-ocular muscles rather than orbital fat; however, there are studies that have shown both fat and muscle reduction with the medication. This study concludes that in patients with high FMR, surgical decompression is favourable, and in those with low FMR, either a surgical or medical approach can be offered. It is difficult to draw real conclusions, however, as the two groups for comparison have fundamental differences including group size, baseline clinical activity score and baseline proptosis. Another source of bias is that the surgical group included patients operated on between 2017–2019, whereas the teprotumumab group are from 2020–2022 (after FDA approval). This not only presents selection bias but also bias in the form of altered practice due to introduction of new treatment as well as the presence of a worldwide pandemic, the impact of which have not been discussed in the paper. Another flaw is the follow-up time for both groups: 30 days for teprotumumab and 3–6 months for decompression. There are studies that show recurrence of proptosis following cessation of teprotumumab, but this can occur months later. Therefore, analysing the level of proptosis in this group at only 30 days is a major flaw in study design and significantly limits the comparisons made with the surgical group where post-treatment proptosis was measured at 3–6 months.

A comparison of proptosis reduction with teprotumumab versus surgical decompression based on fat-to-muscle ration in thyroid eye disease.
Ting MAJ, Topilow NJ, Ediriwickrema LS, et al.
ORBIT
2024;43(2):222–30.