ESR1 and cancer: Women who had ER-positive or PgR-positive cancer rarely had the brain as the first distant metastatic site compared with women whose cancer did not express these proteins (3 (2.1%) of 142 vs. 8 (8.9%) of 90, P = 0.025; 1 (0.9%) of 106 vs. 10 (8.1%) of 124, P = 0.012).