Contemporary hormonal contraception and colorectal cancer in premenopausal women: nationwide cohort study.
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OBJECTIVE: To assess the effect of different types of contemporary hormonal contraceptives on the risk of developing colorectal cancer in women of reproductive age. DESIGN: Nationwide cohort study. SETTING: Denmark based on national registers. PARTICIPANTS: The study included women aged 15-49 years living in Denmark between 1995 and 2021, who had at least five years of residence and no history of cancer, hysterectomy, oophorectomy, or sterilisation. MAIN OUTCOME MEASURES: Adjusted incidence rate ratios with 95% confidence intervals (CIs) for a first time diagnosis of colorectal cancer by type and duration of hormonal contraceptive use. RESULTS: Among 1 956 948 women followed for a median of 12.5 years (24.5 million person years in total), 1878 colorectal cancers were detected. Compared to never users, the incidence rate ratio of colorectal cancer among all current and recent users was 0.94 (95% CI 0.83 to 1.06). The incidence rate ratio with less than five years of use was 0.97 (0.85 to 1.11) and 0.86 with more than 10 years of use (0.62 to 1.18). The incidence rate ratio in previous users was similar to never users, however, with some indication for a decreased incidence rate ratio 10 or more years after cessation (0.81, 95% CI 0.66 to 0.99). No consistent differences in risk between newer and older combined oral contraceptives were observed. The most used progestogen-only pills gave an incidence rate ratio of 1.09 (0.74 to 1.61) and the most used progestogen-only non-oral product, the levonorgestrel releasing intrauterine device, gave an incidence rate ratio of 0.96 (0.81 to 1.15). CONCLUSION: The risk of colorectal cancer was not substantially affected by current or recent use of contemporary hormonal contraception, suggesting that modern products neither protect against nor contribute to the rising incidence in young women. Although some subgroup estimates were imprecise, no support was found for an association between hormonal contraceptive use and colorectal cancer.