ESR1 and breast carcinoma: Another study in which the sequential and concomitant administration of GnRH and chemotherapy were compared in women with ER+ breast cancer revealed that sequential administration was not inferior to concomitant administration in terms of early menopause rate, (cessation of menstruation lasting longer than 12 months after the last chemotherapy or GnRHa dose), with postmenopausal or unknown FSH and estradiol levels (simultaneous vs. sequential: OR, 1.01; 95% CI: 0.50–2.08, p = 0.969; OR, 1.13; 95% CI: 0.54–2.37, p = 0.737).