Study | Group 1 | Incidence of breast cancer in group 1 | Group 2 | Incidence of breast cancer in group 2 | Relative risk (RR) | 95 % confidence interval (95 % CI) |
---|---|---|---|---|---|---|
Espie et al. 2007 [16] | Estradiol + progesterone | 4/999 | Estradiol + synthetic progestina | 12/1272 | 0.42 | 0.13–1.31 |
Fournier et al. 2008 [8] | Estrogen + progesterone (almost exclusively estradiol compounds) | 129/40,537 person-years | Estrogen + synthetic progestin (almost exclusively estradiol compounds) | 635/135,288 person-years | 0.68 | 0.56–0.82 |
Estrogen + progesterone (almost exclusively estradiol compounds) | 129/40,537 person-years | Estrogen + synthetic progestinb (almost exclusively estradiol compounds) | 606/128,253 person-years | 0.67 | 0.76–0.81 |