Trastuzumab-induced optic neuritis: “blindness” side effect

Abstract

Introduction Trastuzumab improved the prognosis of patients with human epidermal growth factor receptor 2 (HER2)+ breast cancer (BC). Here, we present a patient who developed acute vision loss due to optic atrophy in both eyes after trastuzumab. Case report A 60-year-old female patient was diagnosed with locally advanced HER2+ BC in January 2021. After four cycles of neoadjuvant anthracycline-based chemotherapy followed by four cycles of docetaxel, trastuzumab, and pertuzumab combined treatment, the patient underwent a right modified radical mastectomy. Three days after the end of the second cycle of adjuvant trastuzumab, she presented with acute vision loss. The patient's visual acuity was 90% in the right eye and 60% in the left eye. The left eye had optic nerve edema and spindle hemorrhages. First, on suspicion of optic neuritis, the patient was given a 1 gram/day pulse steroid for three days. However, optic neuritis was not considered during the follow-up. Metastasis was considered at the exit of the left optic nerve. Trastuzumab was started by making a mutual decision with the patient. Six days after the sixth dose of adjuvant trastuzumab, she presented with almost complete vision loss. Management and outcome The patient was diagnosed with optic neuritis, and a pulse steroid was administered. Trastuzumab was permanently discontinued. However, the patient's visual acuity in both eyes remained at 5–10%. Discussion Vision loss due to optic neuritis is a devastating side effect. Understanding that trastuzumab-induced optic neuritis may develop will help clinicians detect side effects early and manage them more effectively.