A Novel Gene Mutation of PIK3R1EY451delinsD in Breast Cancer with the Resistance to HER2-targeted Therapy

Previously, little is known about the relationship between the PIK3R1 mutation status and the resistance to HER2-targeted therapies. Herein, we report a HER2-positive breast cancer patient with PIK3R1EY451delinsD showed resistance to HER2-targeted therapy, and adding everolimus to the treatment of trastuzumab and carboplatin achieved better effect.