What type of cancer is reduced in female patients of reproductive age taking oral contraceptives (OCs)?

Oral Contraceptives Reduce Ovarian and Endometrial Cancer Risk

Oral contraceptives significantly reduce the risk of ovarian cancer by approximately 50% and endometrial cancer by 30-50%, with protection lasting decades after discontinuation. 1, 2

Primary Cancer Risk Reductions

Ovarian Cancer Protection

• Oral contraceptives reduce ovarian cancer risk by 45-60%, with the protective effect increasing with longer duration of use 1, 2, 3
• The risk reduction is approximately 29% per 5 years of use for recent users (cessation <10 years ago), 19% for cessation 10-19 years prior, and 15% for cessation 20-29 years prior 3
• This protection persists for more than 30 years after discontinuation, though it becomes somewhat attenuated over time 3
• For every 5,000 woman-years of oral contraceptive use, approximately two ovarian cancers and one death are prevented before age 75 3
• In BRCA1/2 mutation carriers specifically, oral contraceptives reduce ovarian cancer risk by approximately 50% (relative risk 0.51-0.52), with greater protection associated with longer duration of use 1

Endometrial Cancer Protection

• Oral contraceptives reduce endometrial cancer risk by 30-50%, with the protective effect most pronounced after 3 or more years of use 1, 2, 4, 5
• After 10 years of use, the risk reduction reaches 80% 4
• The protective effect remains for at least 20 years after cessation of use 4, 5
• Women who used oral contraceptives for at least 12 months have a relative risk of 0.5 compared to never-users 5
• Approximately 2,000 cases of endometrial cancer are prevented annually in the United States by past and current oral contraceptive use 5
• Formulations with ethinyl estradiol and second-generation progestins show stronger protective effects (HR 0.52 and 0.43 respectively for >5 years use) compared to older formulations 6

Colorectal Cancer

• Decreased risk of colorectal cancer has been demonstrated in oral contraceptive users, though the magnitude is less well-defined than for ovarian and endometrial cancers 1, 2

Breast Cancer Risk Considerations

While oral contraceptives provide substantial cancer protection, clinicians must balance this against a modest increase in breast cancer risk:

• Current or recent users have a relative risk of 1.08-1.24 for breast cancer 1, 7
• This elevated risk completely disappears within 10 years of discontinuation 1, 7
• The absolute risk remains low in young women despite elevated relative risk, as baseline breast cancer incidence is very low under age 34 1, 7
• For women with family history or BRCA1/2 mutations, current evidence does not suggest the baseline increased risk is further amplified by oral contraceptive use 1, 7

Clinical Decision Algorithm

For women considering oral contraceptives, prioritize the substantial and long-lasting ovarian and endometrial cancer risk reductions, which represent mortality benefits that outweigh the temporary and modest breast cancer risk increase in most clinical scenarios. 1, 3

Step 1: Exclude Absolute Contraindications

• Current or recent (<5 years) breast cancer diagnosis is Category 4 (unacceptable health risk) 1, 7
• Age ≥35 years with smoking, hypertension, diabetes, or cardiovascular disease significantly increases thromboembolism and cardiovascular risks 1, 7

Step 2: Identify High-Benefit Populations

• BRCA1/2 mutation carriers benefit substantially from the 50% ovarian cancer risk reduction, which is particularly important given their 30-60% lifetime ovarian cancer risk 1, 7
• Women with Lynch syndrome may benefit from endometrial cancer risk reduction, though they require ongoing surveillance 1
• Nulliparous women show particularly strong endometrial cancer protection (relative risk 0.4) 5

Step 3: Optimize Formulation Selection

• Prefer formulations with ethinyl estradiol and second-generation progestins for maximum endometrial cancer protection 6
• Lower-dose formulations may have more favorable breast cancer risk profiles while maintaining cancer-protective benefits 1, 7

Common Pitfalls to Avoid

• Do not overestimate absolute breast cancer risk in young women: A relative risk of 1.2-1.5 in women under 34 translates to minimal absolute risk increase given the rarity of breast cancer at that age 1, 7
• Do not assume past oral contraceptive use permanently increases breast cancer risk: The risk elevation resolves completely within 10 years of stopping 1, 7
• Do not unnecessarily restrict oral contraceptives in women with family history of breast cancer: Evidence does not support significantly amplified risk in this population 1, 7
• Do not discount the mortality benefit of ovarian cancer prevention: Ovarian cancer has high mortality, and the 50% risk reduction represents a substantial survival benefit that persists for decades 1, 3
• Remember that cervical cancer risk may increase with ≥5 years of use, though this risk declines after discontinuation and disappears after 10 years of non-use 1