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ABSTRACT: Background
Postmenopausal hormone (PMH) therapy may reduce colorectal cancer (CRC) risk, but existing data are inconclusive.Objectives
To evaluate associations between PMH therapy and incident CRC, overall and by molecularly defined subtypes, in the population-based Iowa Women's Health Study of older women.Methods
Exposure data were collected from Iowa Women's Health Study participants (55-69 years) at baseline (1986). Archived, paraffin-embedded tissue specimens for 553 CRC cases were collected and analysed to determine microsatellite instability (MSI-L/MSS or MSI-H), CpG island methylator phenotype (CIMP-negative or CIMP-positive) and BRAF mutation (BRAF-wildtype or BRAF-mutated) status. Multivariable Cox regression models were fit to estimate RRs and 95% CIs.Results
PMH therapy (ever vs never use) was inversely associated with incident CRC overall (RR=0.82; 95% CI 0.72 to 0.93), with a significantly lower risk for MSI-L/MSS tumours (RR=0.75; 95% CI 0.60 to 0.94), and borderline significantly lower risks for CIMP-negative (RR=0.79; 95% CI 0.63 to 1.01) and BRAF-wildtype (RR=0.83; 95% CI 0.66 to 1.04) tumours. For PMH therapy >5 years, the subtype-specific risk estimates for MSI-L/MSS, CIMP-negative and BRAF-wildtype tumours were: RR=0.60, 95% CI 0.40 to 0.91; RR=0.68, 95% CI 0.45 to 1.03; and RR=0.70, 95% CI 0.47 to 1.05, respectively. PMH therapy was not significantly associated with the MSI-H, CIMP-positive or BRAF-mutated CRC subtypes.Conclusions
In this prospective cohort study, PMH therapy was inversely associated with distinct molecularly defined CRC subtypes, which may be related to differential effects from oestrogen and/or progestin on heterogeneous pathways of colorectal carcinogenesis.
SUBMITTER: Limsui D
PROVIDER: S-EPMC3584677 | biostudies-literature | 2012 Sep
REPOSITORIES: biostudies-literature
Limsui David D Vierkant Robert A RA Tillmans Lori S LS Wang Alice H AH Weisenberger Daniel J DJ Laird Peter W PW Lynch Charles F CF Anderson Kristin E KE French Amy J AJ Haile Robert W RW Harnack Lisa J LJ Potter John D JD Slager Susan L SL Smyrk Thomas C TC Thibodeau Stephen N SN Cerhan James R JR Limburg Paul J PJ
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<h4>Background</h4>Postmenopausal hormone (PMH) therapy may reduce colorectal cancer (CRC) risk, but existing data are inconclusive.<h4>Objectives</h4>To evaluate associations between PMH therapy and incident CRC, overall and by molecularly defined subtypes, in the population-based Iowa Women's Health Study of older women.<h4>Methods</h4>Exposure data were collected from Iowa Women's Health Study participants (55-69 years) at baseline (1986). Archived, paraffin-embedded tissue specimens for 553 ...[more]