Case-control study of oestrogen replacement therapy and risk of cervical cancer

Objective: To examine the relation between use of oestrogen replacement therapy and risk of cervical cancer. Design: Case-control study. Setting: Northern Italy. Subjects: 645 women aged 40-75 years with cervical cancer admitted between 1981 and 1993 to university and general hospitals. The control group consisted of 749 women aged 40-75 years admitted to the same hospitals with acute conditions judged to be unrelated to any of the known or suspected risk factors for cervical cancer. Main outcome measures: Use of oestrogen replacement therapy and risk of cervical cancer. Results: 40 cases versus 86 controls had ever used oestrogens, and the corresponding multivariate odds ratio was 0.5 (95% confidence interval 0.3 to 0.8). The odds ratios of cervical cancer decreased with duration of use, being 0.6 (0.4 to 1.1) for less than 12 months' use and 0.5 (0.2 to 1.0) for use for 12 months or more compared with never users. The protection tended to be somewhat stronger for women reporting first oestrogen use before age 50. The odds ratio was 0.9 (0.5 to 1.7) for women who had taken oestrogens within the past 10 years and 0.4 (0.2 to 0.7) for those who had taken them 10 or more years ago. Conclusion: These findings suggest that exogenous oestrogens do not increase the risk of cervical cancer and may decrease the risk.