Colorectal cancer incidence and postmenopausal hormone use by type, recency, and duration in cancer prevention study II.
The Women's Health Initiative randomized trials showed a reduction in colorectal cancer risk with the use of estrogen plus progesterone (E + P), but not with estrogen alone (E-only), after intervention periods <7 years. Using data from the Cancer Prevention Study II Nutrition Cohort, we examined associations of colorectal cancer risk with E-only and E + P, including analyses by recency and duration of hormone use. During 13.2 years of follow-up, 776 cases of invasive colorectal cancer occurred among 67,412 postmenopausal women participants. Cox proportional hazards models were used to estimate multivariate-adjusted relative risks (RR) and 95% confidence intervals (95% CI) of colorectal cancer for current and former hormone users according to hormone type and duration of use. Relative to women who never used postmenopausal hormones, current, but not former, use of E-only was associated with a reduced risk of colorectal cancer (RR 0.76; 95% CI, 0.59-0.97). Among current E-only users, duration of use was inversely and linearly associated with risk (P(trend) = 0.01). Use of E-only for <5 years was not associated with reduced risk, whereas use for >or=20 years was associated with a 45% reduction in risk (RR, 0.55; 95% CI, 0.36-0.86). There were no statistically significant associations between E + P and colorectal cancer risk. Our results suggest a strong inverse association of long-term use of E-only with colorectal cancer risk, underscoring the importance of collecting data on duration of hormone use in epidemiologic studies of postmenopausal hormones and risk of disease.
Hildebrand
Janet S
JS
Department of Epidemiology, American Cancer Society, Atlanta, Georgia 30303, USA. janet.hildebrand@cancer.org
Jacobs
Eric J
EJ
Campbell
Peter T
PT
McCullough
Marjorie L
ML
Teras
Lauren R
LR
Thun
Michael J
MJ
Gapstur
Susan M
SM
D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D017698:Postmenopause; D011374:Progesterone / Q000627:therapeutic use*; D011372:Progestins / Q000627:therapeutic use*; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D016387:Women's Health
D011372:Progestins; D011374:Progesterone