Grand Rounds

Long-Term Oral Contraceptive Use and Cancer Risk

BACKGROUND AND PURPOSE:

Karlsson et al. (Cancer Research, 2020) assessed the time-dependent effects of long-term oral contraceptive use on cancer risk

Observational cohort study (UK Biobank)
Participants
- Women born between 1939 and 1970
Exposure
- Ever use of oral contraceptives
Study design
- Information on cancer diagnoses were collected from self-reported data and from national registers until March 2019

256,661 women
Odds of cancer were lower among ever users of oral contraceptives
- Ovarian cancer: OR 0.72 (95% CI, 0.65 to 0.81)
- Endometrial cancer: OR 0.68 (95% CI, 0.62 to 0.75)
- Association stronger with longer use
- Protective association for above cancers remained significant up to 35 years after last use of oral contraceptives (P<0.001)
Increased breast cancer risk was seen when follow-up was limited to 55 years of age, but not for the full lifespan
- Limited follow-up: OR 1.10 (95% CI, 1.03 to 1.17)
The researchers only found a higher breast cancer risk in former users immediately (≤2 years) after discontinuing oral contraceptive use
- Hazard ratio 1.55 (95% CI, 1.06 to 2.28)

The use of oral contraceptives reduces the risk of ovarian and endometrial cancer
Oral contraceptives effect on the risk of breast cancer over a lifetime is limited
The authors state that this study data

…reflect a shorter latency period for breast cancer in oral contraceptive users, rather than a larger lifetime risk, compared to never users

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