Cancer Risk and Contraception

Introduction to Cancer Risk

• The International Agency for Research on Cancer (IARC) classifies combined oral contraceptives (COCs) as Group 1 carcinogens, indicating sufficient evidence that COCs can cause cancer in humans, specifically an increased risk of breast cancer and cervical cancer 1
• The World Health Organization (WHO) reports that COCs are not associated with increased risk of myocardial infarction in healthy, normotensive, nondiabetic, nonsmokers at any age 1

Increased Cancer Risk

• Current COC users have a relative risk of 1.24 (95% CI, 1.15-1.33) for breast cancer, with risk returning to baseline approximately 10 years after discontinuation 1
• Risk of cervical cancer increases with duration of COC use, particularly with ≥5 years of use, and declines after discontinuation 1, 2

Reduced Cancer Risk

• COCs provide significant protective effects against endometrial cancer 1, 2
• COCs reduce the risk of ovarian cancer, with protection lasting 15-20 years after discontinuation 1, 2
• COCs reduce the risk of colorectal cancer 1

Factors Influencing Cancer Risk

• Age-related factors: Breast cancer risk is highest in women <34 years when the baseline incidence is lowest 1
• Duration of use: Some cancer risks correlate with longer duration of use 1
• Time since discontinuation: Many risks diminish after stopping COCs 1

Progestin-Only Contraceptives (POCs)

• POCs do not appear to increase the risk of venous thromboembolism 3

Guideline Recommendations

• The American College of Obstetricians and Gynecologists (ACOG) and other guideline societies recommend assessing baseline cancer risk factors, considering duration of planned use, and evaluating alternative options when considering birth control and cancer risk 1
• For women with high baseline cancer risk, consider non-hormonal methods, and for women with contraindications to estrogen, consider progestin-only methods 1