Successful Trastuzumab-Deruxtecan Rechallenge After Interstitial Lung Disease: A Case Report.

Trastuzumab deruxtecan (T-DXd) is used to treat human epidermal growth factor receptor 2-positive advanced breast cancer. Interstitial lung disease (ILD) is a severe adverse event associated with T-DXd. Current guidelines recommend permanent discontinuation of T-DXd after Common Terminology Criteria for Adverse Events (CTCAE) grade ≥ 2 ILD. Here, we describe a case of successful rechallenge with T-DXd after CTCAE grade 2 treatment-induced ILD. After discontinuation of T-DXd, ILD was treated with steroids until complete resolution. Given the initial beneficial antitumor response, retreatment was discussed during disease progression. In a shared decision with the patient, T-DXd was restarted at the lowest registered dose, along with low-dose steroids. ILD did not reoccur. Importantly, both clinical and radiological responses to the treatment were observed, with an improvement in the patient's quality of life. This case demonstrates that retreatment with T-DXd after a grade 2 ILD event is feasible and yields clinical benefit.