ESR1 and breast cancer: Furthermore, there were no differences regarding disease free survival (P = 0.664 for ER+ cases and P = 0.391 for ER- cases) and metastasis free survival (P = 0.615 for ER+ cases and P = 0.941 for ER- cases) between patients with HER2- and HER2low breast cancer (Kaplan–Meier curves not shown).