Proptosis Regression After Teprotumumab Treatment for Thyroid Eye Disease

Purpose: This study analyzed the degree and timing of proptosis regression after teprotumumab therapy. Methods: A retrospective study of all patients who completed 8 teprotumumab infusions at 1 institution from January 1, 2020 to December 31, 2022. Change in proptosis was assessed in millimeters and percentages compared with immediate post-treatment and pretreatment proptosis. Results: Of 119 patients with post-treatment data (mean follow-up 10.56 months, range: 3.05–25.08), 208 (87.39%) eyes of 110 patients had initial proptosis improvement. Of the 78 patients with multiple follow-up visits, 102 (65.38%) eyes of 59 patients had proptosis regression averaging 12.78% (range: 1.85–58.82%) compared with immediately post-treatment or 2.43 mm (0.5–10.0 mm). Eight (7.84%) eyes had initial documentation of regression more than 1 year after treatment, 40 (39.22%) between 6 months and 1 year, and 54 (52.94%) eyes within 6 months with 25 (46.30%) of these continuing to worsen at subsequent follow-up. Forty (25.64%) eyes of 24 patients had more proptosis at most recent follow-up than before teprotumumab, with an average regression of 1.53 mm (0.5–4.0 mm) or 7.74% (1.85–20.69%) of pretreatment proptosis. In comparison, 99 (63.46%) eyes of 54 patients maintained improvement, with reduction averaging 3.13 mm (0.5–11.0 mm) or 13.19% (1.92–41.67%) of pretreatment proptosis ( p < 0.001). Conclusions: Two-thirds of eyes had regression despite initial teprotumumab response, typically within 1 year of treatment, with ongoing worsening over time. Most patients maintained some proptosis reduction compared with before treatment despite regression, although 25% were worse than pretreatment. The occurrence of regression was independent of the pretreatment duration of clinical thyroid eye disease. Overall, compared with preteprotumumab, there was a greater amount of improvement than regression at most recent follow-up.