Do Combined Oral Contraceptive Pills (COCPs) increase the risk of breast cancer?

COCP and Breast Cancer Risk

Current or recent use of combined oral contraceptive pills (COCPs) is associated with a small but measurable increase in breast cancer risk, with a relative risk of approximately 1.2-1.6 for current users, though this risk disappears within 10 years of discontinuation. 1

Magnitude of Risk for Current/Recent Users

The evidence consistently demonstrates an elevated breast cancer risk among women actively using COCPs:

• Current users have a relative risk of 1.24 (95% CI, 1.15-1.33) based on a large meta-analysis of 53,297 women with breast cancer and 100,239 controls 1
• More recent systematic reviews show a relative risk of 1.08 (95% CI, 1.00-1.17) for current COCP users 1
• The FDA drug label reports relative risks ranging from 1.19 to 1.33 for current or recent users (within 6 months of last use) 2
• Risk increases with duration of current use, ranging from 1.03 with less than one year of use to approximately 1.4 with more than 8-10 years of continuous use 2

Critical Timing Considerations

The increased risk is temporary and confined to active or very recent use:

• The elevated risk disappears completely within 10 years after discontinuation 1
• Five studies comparing "ever-users" (current or past) versus never-users found no association between past COCP use and breast cancer risk, with effect estimates ranging from 0.90 to 1.12 2
• This temporal pattern suggests the risk is related to active hormonal exposure rather than a permanent carcinogenic effect 1

Age-Specific Risk Patterns

The relative risk increase is paradoxically greatest in younger women, when absolute breast cancer incidence is lowest:

• Women under 34 years have the highest relative risk increase, though their baseline breast cancer incidence remains very low 1, 3
• Among women ages 20-39, current use for ≥5 years shows particularly elevated risks for estrogen receptor-negative (ER-) disease (OR 3.5; 95% CI, 1.3-9.0) and triple-negative breast cancer (OR 3.7; 95% CI, 1.2-11.8) 4
• The absolute risk remains low even with these elevated relative risks due to the rarity of breast cancer in young women 1

Special Populations: Family History and BRCA Carriers

Women with family history of breast cancer or BRCA mutations do not appear to have significantly amplified risk from COCP use:

• Current evidence does not suggest that increased baseline risk for breast cancer among women with family history or BRCA1/2 genes is modified by COCP use 1
• The CDC Medical Eligibility Criteria assigns Category 1 (no restrictions) for women with family history of breast cancer using COCPs 1, 3
• However, data for BRCA carriers remain conflicting, with some studies showing increased risk and others showing no significant association 1, 3
• A systematic review of 10 studies and one pooled analysis of 54 studies found that COCP use does not significantly modify breast cancer risk among women with familial history 5

Contraindications and Clinical Categories

COCPs are absolutely contraindicated in specific breast cancer scenarios:

• Current breast cancer is Category 4 (unacceptable health risk) because breast cancer is a hormonally sensitive tumor and prognosis may worsen with hormonal contraceptive use 1
• Past breast cancer with no evidence of disease for 5 years is Category 3 (theoretical or proven risks usually outweigh advantages) 1
• Undiagnosed breast mass is Category 2 (advantages generally outweigh risks), but evaluation should be pursued as early as possible 1
• Benign breast disease is Category 1 (no restrictions) 1

Balancing Risks with Cancer-Protective Benefits

COCPs provide substantial protection against other gynecologic cancers that must be weighed against breast cancer risk:

• Ovarian cancer risk is reduced by approximately 50% with COCP use 3
• Endometrial cancer risk is significantly reduced with COCP use 1, 3
• Colorectal cancer risk may be reduced by approximately 20% 3
• These protective effects persist long after discontinuation, unlike the temporary breast cancer risk elevation 1

Clinical Decision-Making Algorithm

For women considering COCPs, assess the following in order:

1. Exclude absolute contraindications: Current or recent (<5 years) breast cancer diagnosis 1
2. Evaluate cardiovascular risk factors: Age ≥35 with smoking, hypertension, diabetes, or other cardiovascular disease significantly increases VTE, MI, and stroke risk beyond breast cancer concerns 1, 3
3. Consider age and baseline breast cancer risk: Women under 40 have very low absolute breast cancer risk despite elevated relative risk with COCP use 1
4. Weigh cancer-protective benefits: For women at higher risk of ovarian or endometrial cancer, the protective benefits may outweigh the temporary breast cancer risk elevation 3
5. Assess contraceptive need: FDA approval for all COCPs for acne treatment specifically requires that women also desire contraception 1

Common Pitfalls to Avoid

• Do not overestimate absolute risk in young women: A relative risk of 1.5 in a 25-year-old translates to minimal absolute risk increase given the rarity of breast cancer at that age 1
• Do not assume past COCP use permanently increases risk: The risk elevation is confined to current/recent use and resolves within 10 years of stopping 1, 2
• Do not unnecessarily restrict COCPs in women with family history: Evidence does not support significantly amplified risk in this population 1, 3, 5
• Do not ignore the substantial ovarian and endometrial cancer protection: These benefits often outweigh the temporary breast cancer risk, particularly for women using COCPs long-term 3
• Do not prescribe COCPs solely for acne without contraceptive need: FDA approval requires concurrent desire for contraception 1