Delayed Bleeding With Variable Presentations in Implant-Based Breast Reconstruction During Adjuvant Ado-Trastuzumab Emtansine (Kadcyla) Therapy: Two Case Reports

Ado-trastuzumab emtansine (T-DM1) is an effective adjuvant therapy for human epidermal growth factor receptor 2-positive breast cancer; however, its surgical safety profile remains unclear.We observed delayed bleeding with variable and often subtle clinical manifestations during implant-based breast reconstruction (IBBR).Two patients who received adjuvant T-DM1 therapy after IBBR were retrospectively reviewed.The patient in Case 1 developed a recurrent seroma and liquefied hematoma requiring repeated aspirations, with platelet counts decreasing from 218 10 9 /L to 33 10 9 /L before expander removal.The patient in Case 2 experienced an acute massive hematoma on postoperative day (POD) 2, prior to T-DM1 initiation, which resolved after re-exploration; a temporally distinct delayed hemorrhagic event occurred on POD 175 during T-DM1 therapy after radiotherapy, accompanied by a platelet nadir of 34 10 9 /L.Both patients required plateletpheresis and prolonged drainage.Delayed bleeding during T-DM1 therapy may reflect a combination of hematological suppression and vascular vulnerability.Therefore, vigilant surveillance and cautious postoperative rehabilitation are warranted.