ESR1 and breast cancer: Among HR+ BC patients, those with estrogen receptor (ER)-positive and progesterone receptor (PgR)-positive (ER+ PgR+) disease had significantly longer PFS and OS when treated with CV vs. C (median PFS: 7.28 vs. 5.96 months, p = 0.025; median OS: 27.2 vs. 20.9 months, p = 0.01) (Figure S2A,B), while we found no significant PFS or OS differences among ER+ and PgR-negative (PgR-) BC patients treated with CV vs. C (median PFS: 9.63 vs. 13.08 months, p = 0.53; median OS: 32 vs. 27.7 months, p = 0.87) (Figure S2C,D).