Cyclophosphamide for severe T-DXd-induced interstitial lung disease in low-HER2 breast cancer: a case report and mechanistic insights

This is the first reported case of successful cyclophosphamide treatment for Grade 4 T-DXd-induced ILD in a low-HER2 breast cancer patient with severe liver metastases. It highlights the potential efficacy of cyclophosphamide in treating severe T-DXd-induced ILD, particularly in steroid-refractory cases. The mechanism may involve its ability to inhibit macrophage proliferation and promote anti-inflammatory effects. Further prospective studies are needed to validate the role of cyclophosphamide in managing T-DXd-related ILD and to explore risk stratification for optimal toxicity management.