ESR1 and cancer: Our study also demonstrated that the risk of second primary ovarian cancer was positively associated with the year of first cancer and age at first cancer (56+ years vs. ≤ 45 years, aHR = 1.453, P < 0.001) (Fig. 1c), while an inverse association was found with race (black vs. white, aHR = 0.691, P = 0.001) and ER status (positive vs. negative, aHR = 0.655, P < 0.001) (Fig. 1d), and PR status showed no association with risk (P = 0.060).