PGR and breast cancer: These researchers also conducted a meta-analyses of their results along with another published cohort study, and reported that hazard ratios for high versus low MeD adherence were 0.94 for total postmenopausal breast cancer, 0.98 for ER+, 0.73 for ER−, and 0.77 for ER − progesterone receptor negative breast cancer [16,23,24,25].