Receptor conversion in metastatic breast cancer: a prognosticator of survival

OBJECTIVE This retrospective study investigated the association between hormone receptor (HR) conversion and survival in breast cancer patients. METHODS Estrogen receptor (ER) and progesterone receptor (PR) status (positive or negative) of primary tumors and of paired metastatic sites in 627 breast cancer patients were analyzed by McNemar's test for rates of receptor conversion. A survival analysis was performed using the Kaplan-Meier method, and prognostic factors were assessed using Cox's proportional hazards regression model. RESULTS Conversion of ER occurred in 165 (26.31%) patients, and conversion of PR in 213 (33.97%; P < 0.001, both). For 82 patients whose ER and PR were reassessed 2-4 times during metastatic progression, ER and PR re-conversion occurred in 22 (26.83%) and 29 (35.36%), respectively. The change of ER or PR from positive to negative was associated with worse overall survival and post-recurrent survival (log-rank; P < 0.001, both). A subgroup analysis of HR-positive patients (i.e., positive ER, PR, or both) in primary tumor and HR-negative in metastatic sites showed that patients who accepted both salvage endocrine therapy and chemotherapy had better post-recurrent survival than did those who accepted salvage chemotherapy only (log-rank; P = 0.003). CONCLUSION ER and PR status may change several times during metastatic tumor progression. A change of HR from positive to negative was associated with worse survival compared with consistent positivity. Repeated evaluations of HR status are necessary in metastatic breast cancer. Salvage hormonal therapy is still worth trying for patients whose HR status changes from positive to negative.