Objective: To determine if non-contraceptive oestrogen replacement therapy alters the risk of colorectal cancer.
Data sources: A search was made of the MEDLINE database (January 1974 to October 1993) and Current Contents (October-December 1993) and of reference lists of articles identified in the search. Sixteen studies were identified and fourteen met defined criteria for analysis.
Data synthesis: The overall relative risk of oestrogen replacement therapy use and colorectal cancer was 0.92 (95% confidence interval, 0.74-1.15), which was not significantly different from unity (P > 0.05). The separate overall relative risks of oestrogen replacement therapy use for colon or rectal cancer were also not significantly different from unity.
Conclusion: When the results of all studies published to date are combined, there is no association between oestrogen replacement therapy and the incidence of colorectal cancer. However, long term randomised control trials are required to confirm this.