The pCR rate of TC NAC was not very high despite the high completion rate. TC NAC was effective against the triple-negative subtype, resulting in a higher pCR rate. Therefore, our results indicated that TC NAC showed limited efficacy in luminal subtype breast cancer with the exception of the triple-negative subtype.
141 Background: Recently, docetaxel plus cyclophosphamide (TC) has been established as a standard regimen for adjuvant chemotherapy in HER2- operable breast cancer. However, the efficacy and tolerability of TC as neoadjuvant chemotherapy (NAC) remains unclear. We performed a prospective study of TC NAC in HER2- primary breast cancer. Methods: Eligible patients had HER2- invasive breast cancer that measured more than 1cm, less than 7cm and N0~N1 clinically between July, 2011 and February, 2014. Four cycles of TC(75 and 600 mg/m2) were administered intravenously every 3 weeks as NAC. We investigated the pathological complete response(pCR) of primary breast tumors. pCR was defined as no histological evidence of invasive carcinoma, or the appearance of only ductal carcinoma in situ. The cut-off value of Ki67 index between luminal A and luminal B was defined 20%. Results: We enrolled 52 patients. The completion rate for 4 cycles of TC was 94.2% ( 49 of 52). Relative dose intensity was 99.1% for TC therapy. Forty nine patients were classified according to breast cancer subtype before the estimation. Overall pCR rate was 16.3 %( 8 of 49 ) . pCR rate for patients with luminal A ( ER+, Ki67 low and HER2- ), luminal B ( ER+, Ki67 high and HER2- ) and triple negative ( ER- and HER2- ) were 0%( 0 of 12 ), 4.3 %( 1 of 23 ) and 50.0 %( 7 of 14 ), respectively pCR was achieved in almost triple negative patients. Conclusions: The pCR rate of TC was not so high, regardless of the high completion rate. In this study, TC was effective against triple negative subtype, showing a high pCR rates, compared with luminal subtype. In conclusion, the efficacy of TC NAC in HER2- primary breast cancer is limited, and triple negative subtype might be the good target. Clinical trial information: UMIN000013261.
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