ESR1 and breast cancer: In their meta-analysis of six studies on physical activity and survival after breast cancer diagnosis, Ibrahim and Al-Homaidh found that postdiagnosis physical activity reduced breast cancer deaths by 34%, all cause mortality by 41%, and breast recurrence by 24%; however, when women with estrogen-receptor-negative breast cancer were analyzed separately, there were no significant effects for that sub-group which comprises about one-quarter of women with the disease [34].