Therapeutic effect of taxanes on metastatic breast cancer of various immunohistochemical subtypes.

Taxane drugs play a central role in chemotherapy for breast cancer. However, previous studies have reported that taxanes are relatively ineffective in patients with operable luminal breast cancer compared with other subtypes. Between January 2000 and August 2008, 293 patients with metastatic breast cancer were treated with taxanes in The Cancer Institute Hospital of The Japanese Foundation for Cancer Research and were included in the present study. The patients were divided into 4 subtypes based on the immunohistochemically evaluated estrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor 2 (HER2) status. The clinicopathological features, response rate (RR) and time to progression (TTP) were analyzed retrospectively. In total, 159 patient tissues were classified as luminal type (ER ⁺ and/or PgR ⁺ and HER2 ^- ), 28 patient tissues were classified as luminal-HER2 type (ER ⁺ and/or PgR ⁺ and HER2 ⁺ ), 57 patient tissues were classified as HER2 type (ER ^- , PgR ^- and HER2 ⁺ ), and 49 patient tissues were classified as triple-negative type (ER ^- , PgR ^- and HER2 ^- ). Among the 4 subtypes, the clinical benefit rate was 51.6, 78.6, 71.9 and 40.8%, respectively. There were significant differences in TTP between subtypes (median TTP, 8.3 months in luminal, 14.1 months in luminal-HER2, 10.6 months in HER2, and 4.2 months in triple-negative; P<0.001). Patients with luminal type tumors had a significantly longer TTP than patients with triple-negative type tumors. The present data suggested that the immunohistochemical subtypes were associated with the therapeutic effect of taxanes for metastatic breast cancer and that taxanes yielded an acceptable RR and TTP in luminal metastatic breast cancer. Additional investigations are required to elucidate the predictive markers of taxane therapy for patients with metastatic breast cancer in each immunohistochemical subtype.