ErbB-2 expression does not predict in vitro CMF-chemosensitivity of primary breast tumors

The predictive value of the oncogene product ErbB-2 for chemosensitivity of tumors is still unclear. We therefore correlated the in vitro chemosensiti vity of breast cancer specimens from 125 patients with the respective expre ssion levels of ErbB-2. Twenty-six percent of the patients were premenopaus al Chemosensitivity was tested with the adenosine triphosphate cell viabili ty assay and ErbB-2 content was assessed in the same specimens by ELISA. Wi th the cut-off value used 34 % of the patients had turners with positive Er bB-2 levels. The mean ErbB-2 amount of positive tumors was 388 U/mg +/- 254 and of negative tumors 65 U/mg +/- 36. The mean survival fractions (SF) in the chemosensitivity assay at 0.25 peak plasma concentration (PPC) of a co mbination of cyclophosphamide, methotrexate and 5-fluorouracil (CMF) were n ot significantly, different for. ErbB-2-positive and for ErbB-2-negative tu mors (0.68 and 0.65, respectively (p = 0.6)). The median SF for positive tu mors was 0.68 and for negative tumors 0.62, respectively. Similarly, at fou r times the PPC of CMF no significant differences in SF of ErB-2-positive a nd -negative specimens were found (p = 0.8). Comparison of the median of Er bB-2-protein content of CMF-sensitive tumors with that of CMF-resistant tum ors also yielded no significant difference. Taken together; no significant association between in vitro CMF-chemosensitivity and expression levels of ErbB-2 in tumors of patients with primary chemotherapy naive breast cancer could be determined.