ERBB2 and neoplasm: Using clinical status as proxies for tumor burden, changes in BF-09 serum levels above 30% reflected tumor changes across NAT, AT and MBCT with 74% SE (PD, METS) and 85% SP (PR, CR, NED) for all BC pathologic subtypes and 78% SE and 89% SP for HR+/HER2- only (Table 2).