The 26 % excess of breast cancer is consistent with estimates from
pooled epidemiological data, which reported a 15 % increase for estrogen plus progestin use for less than 5 years and a 53 % increase for use for more than 5 years.32 It is also consistent with the (nonsignificant) 27 % increase found after 6.8 years of follow - up in HERS.33
The researchers
pooled data on 27276 women with endometrial cancer in 36 studies from North America, Europe, Asia, Australia, and South Africa — virtually all the
epidemiological evidence ever collected on the effect of oral contraceptives.