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Estrogen plus progestin use showed greatest reduction in cancer risk
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Sequential estrogen plus progestin use was associated with the largest overall risk reduction for colorectal cancer compared with other hormone therapy formulations and regimens.
Researchers examined cancer risk associated with duration and recency of HT formulations and regimens in postmenopausal women (n=56,733) from the Breast Cancer Detection Demonstration Project follow-up study. They conducted telephone interviews and mailed questionnaires to gather HT use and other risk factor information. Nine hundred sixty women were identified as new cases of colorectal cancer.
There was a decreased risk for colorectal cancer for ever users of unopposed estrogen therapy (RR=0.83; 95% CI, 0.70-0.99), according to the researchers. The largest reduced risk among estrogen users was for current users (RR=0.75; 95% CI, 0.54-1.05) and users of ≥10 years duration (RR=0.74; 95% CI, 0.56-0.96).
There was a greater reduction in risk for users of estrogen plus progestin therapy (RR=0.78; 95% CI, 0.60-1.02), and sequential regimen users (progestin <15 days per cycle) had the greatest reduction (RR=0.64; 95% CI, 0.43-0.95), according to the researchers. The largest risk reduction was observed for past users of ≥five years (RR=0.55; 95% CI, 0.32-0.98).
Cancer Epidemiol Biomarkers Prev. 2009;18:196-203.