Table 1.
Estrogen and breast cancer: findings from selected studies
| Year | First author (reference) | Study design | Finding |
| 1896 | Beatson (1) | Case report | Oophorectomy associated with breast cancer regressions |
| 1968 | Feinleib (2) | Cohort analysis | Oophorectomy associated with lower breast cancer risk |
| 1970 | MacMahon (3) | International collaborative study | Age at first birth related to breast cancer risk |
| 1973 | McGuire (4) | Summary, findings from clinical correlative studies | Estrogen receptor quantitative status correlated with clinical breast cancer response to hormone-directed therapy |
| 1976 | Hoover (5) | Incidence rate in cohort vs rate in general population | Exogenous estrogen alone associated with higher breast cancer risk |
| 1980 | Ross (6) | Case–control analysis | Exogenous estrogen associated with higher breast cancer risk |
| 1983 | Pike (7) | Analysis | Model of endogenous hormonal risk factors with breast cancer |
| 1989 | Bergkvist (8) | Cohort analysis | Exogenous estrogen alone and exogenous estrogen plus progestin both associated with higher breast cancer risk |
| 1995 | Colditz (9) | Cohort analysis | Exogenous estrogen alone and exogenous estrogen plus progestin both associated with higher breast cancer risk |
| 1997 | Collaborative Group on Hormonal Factors in Breast Cancer (10) | Collaborative reanalysis of 51 case–control studies | Hormone therapy (80% exogenous estrogen alone) associated with higher breast cancer risk |
| 2003 | Beral (11) | Cohort analysis with mammography at entry | Exogenous estrogen alone and exogenous estrogen plus progestin both associated with higher breast cancer risk. Trend for higher breast cancer mortality in estrogen plus progestin users |