What is the risk of cancer for a female patient of reproductive age with no significant medical history taking hormonal birth control (hormonal contraceptive)?

Risk of Cancer with Hormonal Birth Control

Hormonal birth control is associated with a small increased risk of breast and cervical cancer, but provides substantial protection against ovarian and endometrial cancer, with the overall cancer risk-benefit profile being neutral to favorable over the long term. 1, 2

Breast Cancer Risk

Current or recent users of combined hormonal contraceptives have a relative risk of breast cancer of approximately 1.20-1.24, representing about 1 extra breast cancer per 7,690 women using hormonal contraception for 1 year. 2, 3

Key Risk Patterns:

• The relative risk increases with duration of use, ranging from 1.09 with less than 1 year of use to 1.38 with more than 10 years of use 3
• The elevated risk completely disappears within 10 years after discontinuation, indicating this is related to active hormonal exposure rather than permanent carcinogenic effects 2, 4
• Women under age 34 have the highest relative risk increase, but their absolute risk remains extremely low due to the rarity of breast cancer in young women 2
• Current breast cancer is an absolute contraindication (Category 4) to hormonal contraceptives because breast cancer is hormonally sensitive and prognosis may worsen 1, 2, 5
• Past breast cancer with no evidence of disease for 5 years is Category 3 (risks usually outweigh benefits) 1, 5

Special Populations:

Women with family history of breast cancer or BRCA1/2 mutations do NOT have amplified risk from oral contraceptives compared to their already elevated baseline risk. 1, 2 Current evidence shows no significant modification of breast cancer risk by oral contraceptive use in BRCA carriers, with meta-analyses showing no significant association 2

Cervical Cancer Risk

Long-term use (≥5 years) of combined hormonal contraceptives may increase the risk of cervical carcinoma in situ and invasive carcinoma among women with persistent HPV infection. 1

• Cervical ectropion is NOT a risk factor for cervical cancer, and restriction of hormonal contraceptive use is unnecessary 1
• Women with cervical intraepithelial neoplasia can use hormonal contraceptives (Category 2) 1
• Cervical cancer awaiting treatment is Category 2, as women may use hormonal contraceptives while awaiting treatment 1

Cancer-Protective Benefits

Ovarian Cancer:

Combined oral contraceptives reduce ovarian cancer risk by 40-60%, with protection increasing with longer duration of use and persisting for at least 10 years after discontinuation. 2, 6, 4

• The risk reduction is approximately 50% for use of one year or more 6
• For BRCA1/2 carriers facing high ovarian cancer risk, oral contraceptives reduce ovarian cancer risk by 45-60%, making them particularly valuable 2
• This substantial benefit is a critical consideration in the overall risk-benefit calculation 2

Endometrial Cancer:

Oral contraceptives reduce endometrial cancer risk by approximately 50% in ever-users, with greater benefit with increasing duration of use. 1, 2, 6, 4

• The protective effect lasts for at least 10 years after discontinuation 6
• Women with endometrial cancer awaiting treatment may use hormonal contraceptives (Category 1) 1

Colorectal Cancer:

Hormonal contraceptive use is associated with reduced colorectal cancer risk. 1, 2

Overall Cancer Balance

Long-term cohort studies with 30+ years of follow-up show an overall neutral balance between short-term cancer risks and long-term cancer benefits in past oral contraceptive users. 1, 2

• A study of 46,022 women in the United Kingdom demonstrated no increased overall cancer incidence or mortality among ever-users 1
• Multiple large prospective cohort studies have not observed increased overall cancer risk 4

Clinical Decision Algorithm

Step 1: Screen for Absolute Contraindications

• Current breast cancer → Do NOT prescribe hormonal contraceptives (Category 4) 1, 5
• Breast cancer with no evidence of disease for <5 years → Generally avoid (Category 3) 1, 5

Step 2: Assess Individual Risk Factors

• Age <35 years with no contraindications → Hormonal contraceptives are appropriate; absolute breast cancer risk remains very low despite small relative risk increase 2
• Family history of breast cancer or BRCA carrier → Hormonal contraceptives are acceptable; evidence does not support amplified risk, and substantial ovarian cancer protection is particularly valuable 1, 2
• Age ≥35 years who smoke ≥15 cigarettes/day → Absolute contraindication due to cardiovascular risk, not cancer risk 1, 5, 7

Step 3: Contextualize Risk Based on Indication

• If prescribed for contraception: Compare risks against those of unintended pregnancy, which carries higher VTE risk (5-20 per 10,000 person-years in pregnancy vs 3-9 in oral contraceptive users) 1
• If prescribed exclusively for acne: Compare risks against those of acne alone, not pregnancy 1

Step 4: Emphasize Protective Benefits

• Counsel patients about the 40-60% reduction in ovarian cancer risk 2, 4
• Counsel about the 50% reduction in endometrial cancer risk 6, 4
• Explain that the small breast cancer risk elevation is temporary and disappears within 10 years of stopping 2, 4

Common Pitfalls to Avoid

• Do NOT overestimate absolute breast cancer risk in young women: A relative risk of 1.2-1.4 in a 25-year-old translates to minimal absolute risk increase (approximately 1 extra case per 7,690 woman-years) given the rarity of breast cancer at that age 2, 3
• Do NOT assume past oral contraceptive use permanently increases cancer risk: The breast cancer risk elevation resolves within 10 years of discontinuation 2, 4
• Do NOT unnecessarily restrict hormonal contraceptives in women with family history or BRCA mutations: Evidence does not support significantly amplified breast cancer risk, and the substantial ovarian cancer protection is particularly valuable in this population 1, 2
• Do NOT ignore the substantial cancer-protective benefits: The 40-60% ovarian cancer risk reduction and 50% endometrial cancer risk reduction are clinically significant and durable 2, 6, 4
• Do NOT require routine cancer screening before initiation: Breast examination, cervical cytology, and other screening tests are not necessary before initiating hormonal contraceptives in asymptomatic women 1, 5