Immune-mediated colitis associated with trastuzumab deruxtecan in ovarian cancer: a case report and rechallenge experience.

Introduction: Low grade serous ovarian tumors present a therapeutic challenge in gynecologic oncology. This has led to increased interest in antibody-drug conjugates such as trastuzumab deruxtecan (T-DXd), which have produced promising responses but carry toxicities potentially limiting their use. Vignette: A patient in her early 50s was initially diagnosed with advanced stage borderline serous ovarian tumor and subsequently developed recurrent low-grade serous ovarian tumor. She progressed on multiple lines of therapy and given HER-2 positivity (IHC 2+), was treated with T-DXd. After her first cycle, she had a remarkable radiographic response; however, she developed intractable nausea, vomiting, and diarrhea leading to hospitalization. Flexible sigmoidoscopy with biopsies supported a diagnosis of drug-induced colitis. She was treated with a methylprednisolone taper, budesonide and infliximab, resulting in resolution of symptoms. She was subsequently re-challenged with a lower dose of T-DXd for cycle 2, which she tolerated well without colitis. Discussion: T-DXd-associated colitis represents a rare toxicity that has not been classified in major clinical trials or prescribing information. In this case, colitis was successfully managed with corticosteroids and infliximab, allowing for safe re-challenge at a reduced dose. This case highlights the importance of recognizing and managing rare toxicities associated with antibody-drug conjugates to optimize their safe use in ovarian cancer treatment.