Molecular Classification of Breast Cancer Tumours from Patients Treated with Doxorubicin and Docetaxel

It is known that four main molecular breast cancer subtypes have different prognoses and different responses to therapy. Luminal A tumours have a better prognosis and they tend to be sensitive to anti-estrogen drugs. Luminal B tumours have incomplete sensitivity to endocrine therapy. Her2 tumours, which have an aggressive natural history, are sensitive to trastuzumab. Finally, basal-like tumours might be eligible for chemotherapy. The aim of this study was to evaluate the chemosensitivity to docetaxel and doxorubicin of breast cancer subtypes. Patients with locally advanced breast cancer were randomized to receive 4 cycles of full dose doxorubicin (75 mg/m2) or docetaxel (100 mg/m2). After the fourth cycle, patients were submitted to surgery to ascertain pathological response. Treatment response was assessed according to Symmans classification. Among 130 samples analysed most ER positive tumours were luminal subtype. 41% of Her2 positive tumours assessed by immunohistochemistry and FISH were Her2 according to the gene expression profile. Luminal A and normal-like tumours have low expression of proliferation genes as well as ki67, whereas Her2 and basal-like tumours are highly proliferative. Both treatments have the same efficiency (20% of responses). However, basal tumours have the poorest outcome in the doxorubicin branch (0% of responses) while they are the most sensitive to docetaxel (50% of responses). Luminal and normal-like tumours have the poorest responses to both treatments. Finally, Her2 tumours had similar outcome in both branches (20% of responses). Genomic classification may assist the physician to choose a specific treatment based on the sub-type of tumour. This study provides the basis for building individualized neoadjuvant therapies for breast cancer.