In a recent meta-analysis, Poggio and colleagues pooled data from four of the five prospective randomized trials; HABITS,206 the Stockholm Study,204 the LIBERATE trial,207 and a small prospective clinical trial by Vassilopoulou-Sellin et al68 that had reported no increased risk of recurrence in women with a history of ER negative breast cancer using estrogen-only HT. Here, ESR1 is linked to breast cancer.