Anthracyclines in basal breast cancer: The NCIC-CTG trial MA5 comparing adjuvant CMF to CEF

519 Background: MA5 randomized premenopausal women with node-positive early breast cancers to cyclophosphamide- methotrexate-fluorouracil (CMF) or cyclophosphamide-epirubicin-fluorouracil (CEF) adjuvant chemotherapy. This and other trials have shown that adjuvant regimens containing anthracyclines confer significant survival benefit to breast cancer patients. Meta-analyses have revealed most benefit in women with HER2(+) or TOPO2 (+) tumors. Population-based data suggest that patients with a core basal phenotype (negative for hormone receptors and HER2, positive for CK5/6 or EGFR) conversely have worse survival on anthracycline containing vs. CMF regimens. Here we test the hypothesis specified a priori that for basal breast cancers anthracyclines may be inferior, using data from MA5. Methods: From 710 patients in MA5, blocks suitable for tissue microarray construction were recovered for 549. Immunohistochemistry for ER, PR, HER2, Ki67, CK5/6 and EGFR was obtained, allowing stratification of 511 cases into intrinsic biological subtypes by published methods (Cheang MC et al. Clin Cancer Res 2008;14:1368–76). Prespecified analyses were conducted independently by the NCIC- CTG statistical centre. Results: In the CEF arm, patients with core basal tumors had a hazard ratio of 1.8 (log rank p=0.02) for overall survival (OS) relative to the other biological subtypes. In the CMF arm, there was no significant difference (HR 0.9, p = 0.7). The interaction between core basal status and treatment was borderline significant (p=0.06). Relapse free survival differences did not reach significance. Conclusions: Data from this randomized trial supports the hypothesis that anthracycline containing adjuvant chemotherapy regimens are inferior to adjuvant CMF in women with basal breast cancer. [Table: see text] No significant financial relationships to disclose.