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.