ESR1 and breast cancer: It could be hypothesized that this might be caused by the abscopal effect, which means that the radiation of a tumor can activate an antitumor immune response.66 In addition, ER+ patients with ductal carcinoma in situ had significantly higher incidences of second primary tumors than patients with stage T1 tumors (HR 1.19, p < 0.0001).65 Progesterone receptor status did not influence the rate of a secondary primary breast cancer.