PIK3CA as a predictor of the clinical efficacy for epirubicin plus docetaxel neoadjuvant chemotherapy in breast cancer.

Abstract

113 Background: PIK3CAgene mutations are the most common activating mutations in human breast cancer (BC). Its association with the resistance to herceptin in HER2-positive BC was reported, but whether it’s related to the efficacy of neoadjuvant chemotherapy is unknown. Methods: We reviewed records of 108 patients with BC treated with epirubicin plus docetaxel neoadjuvant chemotherapy between June 2005 and April 2011. 92 patients’ clinical and pathologic objective response data were collected. FFPE tumor biopsies obtained at the time of diagnoses (and before treatment) were collected. EGFR, KRAS, BRAF, PIK3CA mutations and HER2, PTEN, EGFR mRNA expression were analyzed by liquidchip technology. Chi-square test and Fisher’s exact test were used in statistical analysis. A p value less than 0.05 was considered statistically significant. Results: No mutation was detected in EGFR, KRAS and BRAF. The mutation rate of PIK3CA was 35.1% (38/108), and mutation rates of E542K, E545K, H1047L and H1047R were 3.7, 10.2, 3.7 and 17.6% respectively. More PIK3CA mutations were detected in HER2 high expression tumors (p=0.018). No correlation was found between PIK3CA mutations and PTEN, EGFR expression. Clinical response (CR+PR, 63/92) was associated with PIK3CA mutations (p=0.002). However, PIK3CA mutations rate between pathologic complete release (pCR, 7/92) and non-pCR group was not significantly different (p=0.422). Conclusions: PIK3CA mutation may predict better clinical response in BC patients treated with epirubicin plus docetaxel neoadjuvant chemotherapy. More studies are needed to validate these results and the correlation between PIK3CA mutations and pCR.