Risk of endometrial cancer after treatment with oestrogens alone or in conjunction with progestogens: results of a prospective study.

Use of oestrogens without progestogens is associated with a twofold to threefold increase in risk of endometrial neoplasia. Use of progestogens either removes this increased risk or delays its onset. A further follow up of the cohort is essential to analyse the risks with greater statistical power.