ERBB2 and neoplasm: Systemic delivery of T-DM1 in combination with oncolytic VSV delayed tumor progression in HER2-overexpressing, but trastuzumab-refractory, JIMT1 human breast cancer xenografts compared to monotherapies, underscoring the potential of this combination in treating both oncolytic virus- and trastuzumab-refractory malignancies.