Female patients (n=371) with metastatic breast cancer were treated with endocrine or chemoendocrine therapy as the first-line treatment. Clinical prognostic factors for response and survival were compared between the treatments, including age of the patients, menopausal status, estrogen receptor (ER), disease-free interval (DFI), dominant site of metastasis, number of metastatic organs, performance status (PS), and prior therapy. Although a significantly higher response rate was obtained by the chemo-endocrine therapy compared with the endocrine therapy, the median survival time of patients in endocrine therapy was much longer than those in chemo-endocrine therapy. Multivariate analyses with the logistic regression model showed that in women treated with endocrine therapy ER was shown to be the sole determinant for response, while PS and dominant site of metastasis were selected to be influential in chemotherapy group. For overall survival, the Cox proportional hazard model analysis showed that by endocrine therapy, ER and dominant site were significant determinants of survival, but that of chemotherapy the survival was determined by PS, dominant site, and age of the patients. When response to therapy was included in the Cox survival analysis at the time of 3-month after therapy in the landmark method, the response was the most important factor for survival in both treatment groups, however dominant site in endocrine therapy, and dominant site, PS, and age in chemo-endocrine therapy significantly modified survival. It is concluded that endocrine therapy and chemo-endocrine therapy have different determinants for response and survival in metastatic breast cancer, and that in the survival analysis treatment modality should be included as a prognostic factor.

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