Triple HER2-blockade with lapatinib, trastuzumab, and pertuzumab for treatment of HER2 positive metastatic breast cancer with lymphangitic carcinomatosis: A case study

There are many options for treating human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC), and the best sequential or salvage treatment is still debated. This report outlines a case of a 59 year-old woman with HER2-positive MBC. She received HER2 triple blockade treatment using lapatinib, trastuzumab, and pertuzumab. Before triple blockade treatment, she had already received a total of 10 anti-HER2 therapy regimens in 14 years. Worsening lymphangitic carcinomatosis was determined by computed tomography (CT) in January 2020, as evidenced by dyspnea on exertion, and combination treatment with lapatinib, trastuzumab, and pertuzumab was initiated. After five cycles of combination treatment, CT and chest radiography demonstrated significant improvement in lymphangitic carcinomatosis. The dose of lapatinib was reduced at the third cycle and discontinued because of an adverse event of grade 3 diarrhea. In this case, HER2 triple blockade showed a dramatic response for treating lymphangitic carcinomatosis in a patient with heavily treated HER2-positive MBC.