Reproductive factors and risk of colorectal polyps in a colonoscopy-based study in western Washington State

Oral contraceptives (OC) are associated with a decreased risk of colorectal cancers; however, a recent study reported an increased risk of small colorectal adenomas associated with OC use. To determine if these results were replicable in a different study population, we investigated the relationship between OC use and other reproductive factors and risk of colorectal polyps in a case-control study in western Washington.

Study participants were 24-79-year-old female enrollees at an integrated health care system in western Washington who were diagnosed as having adenomas (n = 299), serrated polyps (n = 337), both types of polyps (n = 105) or as polyp-free controls (n = 615) through an index colonoscopy and completed a structured interview to collect reproductive history information. Multivariable polytomous logistic regression was used to compare case groups to controls and to each other; odds ratios (OR) and 95% confidence intervals were estimated.

There was no association between OC use, duration of use, or recency of use and the risk of either adenomas or serrated polyps [adjusted OR for OC ever use (95% CI) 0.85 (0.58-1.23) and 0.96 (0.66-1.40), respectively], and associations did not differ by lesion severity within the adenoma or serrated pathways. Further, no associations were observed between other reproductive factors and risk of colorectal polyp subtypes.

Our results suggest that reproductive factors, including OC use, are not associated with early colorectal cancer precursor lesions.