In this study, physicians from Quebec, Canada, examined the effects of oral and transdermal estrogen replacement therapy on the risk of colorectal cancer.
The team identified 1197 new cases of colorectal cancer, diagnosed between 1992 and mid-1998, using the Saskatchewan Cancer Agency cancer registry.
They included all women ≥ 50 years of age, who were eligible for coverage by the Saskatchewan Prescription Drug Plan.
|Duration of transdermal estrogen use:|
- < 3 years = OR 0.69
- 3 years = OR 0.33
|British Journal of Cancer|
The team matched 4 controls to each case using incidence density sampling.
The outpatient prescription drug plan database was used to ascertain estrogen prescriptions.
The women were classified according to history of transdermal (TDE) and oral (OE) estrogen use.
When compared with women who had never used HRT, the team found that the odds ratios for <3 and 3 years of TDE use and colorectal cancer were 0.69 and 0.33.
For OE use, odds ratios were 0.90 and 0.75, respectively.
Dr Csizmadi's team concluded, "The risk reduction for colorectal cancer with TDE may be greater in magnitude than that which has been reported for oral HRT".