Dual HER2 Suppression with Lapatinib plus Trastuzumab for Metastatic Inflammatory Breast Cancer: A Case Report of Prolonged Stable Disease

BACKGROUND: Continuous therapy targeting human epidermal growth factor receptor 2 (HER2) is recommended until disease progression for patients with HER2-overexpressing (HER2+) metastatic breast cancer. Prolonged stable disease has been observed with such maintenance therapy using trastuzumab, but the frequency of these cases remains low. Whether combined maintenance therapy with two different HER2-targeted agents could improve the rates of durable progression-free survival compared with trastuzumab alone is under investigation. OBJECTIVES: To evaluate the efficacy of the combined HER2-targeted agents, trastuzumab and lapatinib, as maintenance therapy in one patient. METHODS: We describe a patient with HER2+, hormone receptor-negative, inflammatory metastatic breast cancer who was previously treated with doxorubicin, cyclophosphamide, and zoledronic acid followed by paclitaxel and trastuzumab. After completion, the patient underwent a bilateral mastectomy and then enrolled into a Phase III open-label clinical trial of trastuzumab plus lapatinib. RESULTS: The patient experienced long-term stable disease on combined lapatinib and trastuzumab maintenance therapy over 4 years. CONCLUSIONS: This case demonstrates that prolonged stable disease is possible with lapatinib plus trastuzumab, even in patients with the aggressive inflammatory subtype. Optimization of maintenance therapy could improve outcomes for patients with HER2+ metastatic breast cancer.