The effect of hormone replacement therapy on the risk of colorectal cancer in postmenopausal women /

In this thesis we examine the effect of hormone replacement therapy (HRT) on the risk of colorectal cancer. Also examined are the effects of oral versus transdermal estrogen replacement therapy, methods of defining estrogen exposure, selection bias, and trends in the use of HRT over the last two decades.A nested case-control study was conducted using records from Saskatchewan Health's administrative databases. Information on covariates not available from the databases was collected during interviews, from a subgroup of subjects. Incidence density sampling was used to age match controls (four per case, N = 12,116) to each of 3,059 cases accrued in the province from 1981 to 1998.Short and long durations of HRT use (<5 years and &ge;5 years) were associated with odds ratios (OR) of 0.86 (0.76--0.97) and 0.78 (95% CI: 0.64--0.86), respectively. Stratification according to history of having had a screening sigmoidoscopy did not eliminate the observed protective effect. Important differences were not seen between more recent HRT use (<5 and