The Influence of Basal Phenotype on the Metastatic Pattern of Breast Cancer

Aims To assess whether basal phenotype influences the metastatic pattern and survival in patients with metastatic breast cancer. Materials and methods The basal phenotype status of a well-characterised series of consecutive primary operable breast cancers (1868 cases) was ascertained using the basal cytokeratin markers CK5/6 and CK14. Follow-up data, including time, site and pattern of distant metastasis and post-metastasis survival, were available for 113 women with basal phenotype cancers and they were compared with 178 matching cases from women in the non-basal phenotype group. Results Patients with basal phenotype were more likely to present with intrapulmonary (25/48, [52%] vs 15/64, [23%]; P=0.0009) and/or brain metastases (20/113, [18%] vs 3/178, [2%]; P<0.0001) than non-basal phenotype patients. Patients with non-basal phenotype were more likely to present with bone metastases in the absence of visceral disease (48/102, [47%] vs 14/62, [23%]; P=0.0017) than patients with basal phenotype. There was no significant difference in the frequency of pleural or liver metastases between both groups. Basal phenotype was also associated with a shorter median survival with metastatic disease (10.1 months vs 25 months, P<0.001). The multivariate analysis, including other established prognostic variables in breast cancer, showed that basal phenotype is an independent poor prognostic factor. Conclusion Intrapulmonary and brain metastases are seen more frequently at metastatic presentation in basal phenotype breast cancer patients, and the basal phenotype is associated with a poorer survival after metastatic presentation. Assessment of basal cytokeratin expression status may provide valuable prognostic information relevant to breast cancer patients' management.