Background: The latest clinical trials indicate better performance of aromatase inhibitors, compared to tamoxifen, in adjuvant hormonotherapy of breast carcinoma. The identification of molecular markers, predicting resistance to tamoxifen, could help to identify patients, which are most likely to benefit from aromatase inhibitors in up-front adjuvant hormonotherapy.
Material and methods: Tissue microarrays were constructed from archival paraffin blocks of primary tumors of 179 patients with estrogen receptor positive operable breast carcinoma in stage I-III, subsequently treated with tamoxifen for five years or until relapse, with at least 7 years follow up available. The amplifications of Her-2 and cyclin D1 genes were evaluated by fluorescence in-situ hybridization. The level of progesterone receptor (PR) and Ki67 were estimated by immunohistochemistry.
Results: 54 of above patients recurred during follow up. In univariate analysis of disease free survival, the presence of more than three nodal metastases (RR=4,5 p<0,001), grade 3 (RR=2,3 p=0,035), cyclin D1 (RR=3,06 p<0,001) and Her-2 (RR=3,06 p<0,001) amplifications were identified as significant risk factors, together with the negativity of PR (RR=2,1 p=0,013). In multivariate analysis, only clinical stage III (RR=2,6 p=0,003), cyclin D1 (RR=2,7 p=0,001) and Her-2 (RR=2,1 p=0,014) amplifications proved significant. In 77 patients who received adjuvant chemotherapy no statistically significant risk factor was identified. In multivariate analysis of 102 patients without adjuvant chemotherapy only stage III (RR=6,9 p=0,001) and Her-2 amplification (RR=4,5 p=0,001) were confirmed.
Conclusion: The advanced clinical stage, cyclin D1 and Her-2 gene amplifications represent factors, predicting the failure of adjuvant tamoxifen treatment, but their predictive value is much lower in patients receiving adjuvant chemotherapy. This fact indicates, they can reflect the common biological aggressiveness of tumor and need not to be tamoxifen specific.