C-myc as a predictive marker for chemotherapy in metastatic breast cancer.

C-myc is considered to have an important role in cancerogenesis and tumor progression. The aim of this study was to evaluate a possible significance of c-myc amplification as a clinically useful prognostic/predictive parameter in metastatic breast cancer (MBC). Eighty-seven MBC patients with known clinicopathological parameters were included in the study, at the time of diagnosis of metastatic disease. In metastatic setting, 52% of patients received CMF, 34% received FAC, and 32% received hormonal therapy (tamoxifen). C-myc amplification was analyzed by chromogenic in situ hybridization, according to the manufacturer's instructions. C-myc amplification was detected in 26% cases and showed a strong correlation with ER status, stage of disease (initial) and existence of distance metastasis. There was no statistically significant difference in MBC (post-relapse) survival between c-myc-nonamplified and c-myc-amplified subgroups regardless of or regarding the treatment. However, correlation was found between c-myc status and individual patient's outcomes. Patients with c-myc amplification treated with chemotherapy (CMF and FAC) had clinical benefit (complete remission, partial remission or stable disease) in contrast to patients without amplification. Lack of significant difference in MBC (post-relapse) survival according to c-myc status could be due to a better response of patients to appropriate treatment (chemotherapy). It is possible that negative prognostic impact of c-myc amplification is masked with increased responsiveness to chemotherapy.