Kainan Wang1, Ye Hu1, Lingzhi Xu1, Shanshan Zhao1, Chen Song1, Siwen Sun1, Xuelu Li2, Man Li3. 1. Department of Oncology & Breast Surgery, The Second Hospital of Dalian Medical University, Dalian, 116023, Liaoning Province, China. 2. Department of Oncology & Breast Surgery, The Second Hospital of Dalian Medical University, Dalian, 116023, Liaoning Province, China. dmulixuelu@163.com. 3. Department of Oncology & Breast Surgery, The Second Hospital of Dalian Medical University, Dalian, 116023, Liaoning Province, China. man_li@dmu.edu.cn.
Abstract
BACKGROUND: Resistance to HER2-targeted therapy is a critical issue in breast cancer that must be addressed immediately. PIK3R1 mutations are more common in Chinese breast cancer patients (17%, 25/147, Fudan University Shanghai Cancer Center FUSCC vs. 1.8%, 87/4602, TCGA all breast cancer studies). However, very limited information is available on the relationship between PIK3R1 mutation status and resistance to HER2-targeted therapies in patients with HER2-positive breast cancer. CASE REPORT: We present a case of a HER2-positive advanced breast cancer patient with the PIK3R1EY451delinsD mutation who developed resistance to HER2-targeted therapy and had a better response to everolimus combined with trastuzumab and carboplatin. CONCLUSIONS: To the best of our knowledge, this is the first study to show that the PIK3R1EY451delinsD mutation confers resistance to anti-HER2 therapy in breast cancer and that combining with everolimus treatment may overcome this resistance mechanism. We hypothesize that the PIK3R1EY451delinsD mutation is associated with the resistance to anti-HER2 therapy, and that this mutation merits further investigation as a clinical biomarker and therapeutic target.
BACKGROUND: Resistance to HER2-targeted therapy is a critical issue in breast cancer that must be addressed immediately. PIK3R1 mutations are more common in Chinese breast cancer patients (17%, 25/147, Fudan University Shanghai Cancer Center FUSCC vs. 1.8%, 87/4602, TCGA all breast cancer studies). However, very limited information is available on the relationship between PIK3R1 mutation status and resistance to HER2-targeted therapies in patients with HER2-positive breast cancer. CASE REPORT: We present a case of a HER2-positive advanced breast cancer patient with the PIK3R1EY451delinsD mutation who developed resistance to HER2-targeted therapy and had a better response to everolimus combined with trastuzumab and carboplatin. CONCLUSIONS: To the best of our knowledge, this is the first study to show that the PIK3R1EY451delinsD mutation confers resistance to anti-HER2 therapy in breast cancer and that combining with everolimus treatment may overcome this resistance mechanism. We hypothesize that the PIK3R1EY451delinsD mutation is associated with the resistance to anti-HER2 therapy, and that this mutation merits further investigation as a clinical biomarker and therapeutic target.