The Study Of PIK3CA Mutations In Breast Cancer With Axillary Lymph Node Metastasis

Objective:To explore the mutation status of phosphatidylinositol 3-kinase catalytic alpha(PIK3CA)in breast cancer with axillary lymph node metastasis,and to analyze its correlation with clinicopathological characteristics and efficacy of neoadjuvant chemotherapy.As to provide theoretical basis for individualized treatment of breast cancer.Methods:We collected 81 breast puncture tissues from breast cancer with axillary lymph node metastasis and 20 surgical excision tissues from breast fibroadenoma.All specimens were collected from patients in breast surgery department of the First Hospital of Jilin University from November 2016 to November 2018.All patients signed the informed consent for breast cancer-related gene detection before hollow needle aspiration biopsy of breast tumors or surgery.After extracting DNA from all tissues,we constructed the library of DNA samples which were qualified after concentration determination,prepared the template and enriched them.Then we sequenced them using Ion Proton sequencing platform.NextGENe software with parameters was used to analyze the data and obtain the mutation results of PIK3 CA.All patients with axillary lymph node metastasis of breast cancer received surgery after completing the anticipated regimen of neoadjuvant chemotherapy.And we supplemented the corresponding clinical and pathological data.All data wereanalyzed by SPSS22.0 software.Chi-square test or Fisher’s exact text was used to compare the differences between groups.The statistical results with P<0.05 were statistically significant.Results:In 81 cases of breast cancer with axillary lymph node metastasis,PIK3 CA mutation was detected in 30 cases(mutation rate was 37.0%),mutation frequency was 6.4%-51.5%.No PIK3 CA mutation was detected in 20 cases of breast fibroadenoma in the control group.The mutation rate of PIK3 CA in HER-2 overexpressed breast cancer was higher(60% versus 26.8%,P=0.004).There was no significant correlation between PIK3 CA mutations and age,menstrual status,tumor diameter,lymph node status,clinical stage,ER/PR status,Ki-67 status and molecular typing(P>0.05).After neoadjuvant chemotherapy,the effective rate was 66.7%,lymph node negative rate was22.2%,and pathologic complete response(pCR)rate was 18.5%.There was no significant correlation between PIK3 CA mutations and Miller-Payne grade,lymph node status and pCR of breast cancer after neoadjuvant chemotherapy(P>0.05).Conclusion:(1)In this study,the mutation rate of PIK3 CA in breast cancer with axillary lymph node metastasis was 37.0%.All mutations were located in exon9 or 20,and the mutation rate of exon 20 was higher than that of exon 9.(2)The mutations of PIK3 CA in breast cancer with axillary lymph node metastasis are significantly associated with the over-expression of HER-2.(3)The mutations of PIK3 CA in breast cancer with axillary lymph node metastasis has no significant correlation with the efficacy of neoadjuvant chemotherapy.