Relationship of Ki-67 proliferative index and metastatic tumor of breast cancer.

e22190 Background: The metastatic breast tumor tends to be more aggressive with high proliferation, but this has not been proven in clinical sampling of metastatic tumors. Methods: Forty-eight patients who had histological specimens of both primary and metastatic sites of luminal breast cancer (ER and/or PgR positive and HER2 negative) were examined. We classified them as luminal A (LA) with Ki-67 labeling index of less than 14% and as luminal B (LB) with Ki-67 labeling index of more than 14%. We analyzed their overall survival (OS) and progression free survival (PFS) of 1st line treatment of each subtype of primary and metastatic tumors. Results: Subtypes of primary tumors and metastatic tumors were as follows; the primary tumor: LA; 34 patients (70.8%), LB; 14 (29.2%), metastatic tumors: LA; 21 (43.8%), LB; 27 (56.2%). Patients with LA of the primary tumor demonstrated statistically longer OS (LA; 72.5 months, LB 39.6 months, p=0.009). OS depended on the subtype of the primary tumor. In contrast, patients with LB of a metastatic tumor showed a statistically worse PFS (LA; 20.5 months, LB; 11.5 months, p=0.040). PFS of the 1st line treatment for MBC depended on the subtype of the metastatic tumor. Conclusions: The frequency of LB was increased on metastatic tumors and tended to acquire a higher proliferation index. This suggests that characterization of metastatic tumors could be better as an indicator of subsequent treatment for MBC. [Table: see text]