Premedication With Dexamethasone for Preventing Interstitial Lung Disease in Patients With Breast Cancer Treated With Trastuzumab Deruxtecan

Trastuzumab deruxtecan (T-DXd) has recently received approval as an antibody-drug conjugate for treating patients with metastatic breast cancer (BC) who have HER-2 protein expression as determined by immunohistochemistry, including HER2-positive, -low and -ultralow BC. Its use has shown significant effectiveness in terms of response and survival rates. Pulmonary toxicity, specifically interstitial lung disease (ILD), is of significant clinical interest in 10-15% of patients. For cases of mild toxicity, namely grade 1, the diagnosis relies exclusively on radiological findings in the absence of symptoms. In such cases, T-DXd is temporarily stopped and steroids might be used as treatment. Once the radiological findings have been resolved, the drug can be resumed. Grade 2 is distinguished by the presence of clinical signs such as difficulty breathing and coughing, as well as radiological evidence. In such instances, the medication must be permanently stopped. As a consequence, it is recommended that patients receiving T-DXd treatment should be closely monitored with high-resolution (HR) CT scans every 6-12 weeks. The precise mechanism responsible for this toxicity has not yet been fully elucidated; but it is thought to be inflammatory in origin The risk factors for ILD include lower baseline SpO2, lung comorbidities, reduced renal function, time from initial diagnosis, and drug dose. Administering dexamethasone as a premedication twice a day from the day before T-DXd infusion (D-1) through day 4 (D4) may lower ILD incidence and help prevent permanent T-DXd treatment discontinuation. Primary objective To assess the efficacy of dexamethasone premedication in reducing the occurrence of ILD \>G1 in breast cancer patients receiving T-DXd treatment.