ERBB2 and breast carcinoma: Other reported prognostic factors for shorter TTBM included higher disease burden (i.e., ≥ 2 metastatic sites) [31], higher HER2 levels (measured by the HERmark® Breast Cancer Assay) [21], distant relapse in ≤2 years [22], first distant relapse at a visceral site [23], and nodal involvement [26].