More importantly, upregulated DNA repair has been suggested to be a radioresistance mechanism in HER2-overexpressing tumors, and in vitro studies using the dual EGFR/HER2 inhibitor lapatinib showed about 100% more residual DNA damage foci by combined treatment compared to IR alone in HER2-overexpressing SKBR3 cells (BC) [18]. Here, EGFR is linked to breast cancer.