Does removal of the ovaries (oophorectomy) decrease the risk of breast cancer?

Ovarian Removal and Breast Cancer Risk Reduction

The answer depends critically on whether you carry a BRCA1 or BRCA2 mutation—if you do, removing your ovaries before age 50 can reduce breast cancer risk by approximately 45-56%, but recent high-quality evidence shows this benefit may not exist for women without these mutations or when surgery occurs after age 50.

For BRCA1/2 Mutation Carriers

Evidence of Breast Cancer Risk Reduction

The evidence for breast cancer risk reduction after oophorectomy is strongest and most consistent in women with BRCA1/2 mutations:

• BRCA1 carriers who undergo risk-reducing bilateral salpingo-oophorectomy (RRSO) experience approximately 56% breast cancer risk reduction (OR 0.44; 95% CI 0.29-0.66) 1
• BRCA2 carriers show approximately 43-46% breast cancer risk reduction after RRSO 1
• A meta-analysis demonstrated approximately 50% breast cancer risk reduction across BRCA1/2 carriers following RRSO 1

Critical Timing Considerations

Age at surgery dramatically impacts effectiveness:

• Greatest benefit occurs when RRSO is performed at age ≤40 years in BRCA1 carriers (OR 0.36; 95% CI 0.20-0.64), representing a 64% risk reduction 1
• Moderate benefit at ages 41-50 years in BRCA1 carriers (OR 0.50; 95% CI 0.27-0.92) 1
• No significant benefit after age 50-51 years (the age of natural menopause), as RRSO does not substantially decrease breast cancer risk when performed after this age 1

Important Mortality Benefits

Beyond breast cancer risk reduction, RRSO provides substantial survival advantages:

• 77% reduction in all-cause mortality in BRCA mutation carriers 2, 3
• 60% reduction in breast cancer-specific mortality (HR 0.44) 1
• 79% reduction in ovarian cancer-specific mortality (HR 0.21) 1

For BRCA1 carriers diagnosed with breast cancer, oophorectomy after diagnosis reduces breast cancer mortality by 62% (HR 0.38; 95% CI 0.19-0.77), particularly dramatic in estrogen receptor-negative breast cancer (HR 0.07; 95% CI 0.01-0.51) 4

Evolving and Contradictory Evidence

The Controversy in Recent Studies

A critical shift occurred in studies published after 2016:

• A large Dutch prospective cohort study (N=822) found no statistically significant difference in breast cancer incidence between BRCA1/2 carriers who underwent RRSO versus those who did not 1
• Investigators attributed earlier positive findings to methodological biases, specifically "immortal person-time bias" (counting cancer-free time before surgery as if patients had already had surgery) 1
• A meta-analysis of 19 studies showed protective effects in studies published before 2016, but not in the 3 studies published in 2016 or later 1

Studies Correcting for Bias

When researchers corrected for immortal person-time bias:

• One analysis still found protective effect (HR 0.59; 95% CI 0.42-0.82) 1
• However, another study treating RRSO as a time-dependent variable found no association with breast cancer risk 1

Most Recent High-Quality Evidence (2020)

A 2020 study of 853 premenopausal BRCA carriers showed:

• BRCA1 carriers: 55% breast cancer risk reduction with premenopausal RRSO (HR 0.45; 95% CI 0.22-0.92) 1
• BRCA2 carriers: No significant benefit (HR 0.77; 95% CI 0.35-1.67) 1

This study specifically addressed event-free time bias by beginning observation 6 months after genetic testing 1

Stratified Analysis by Age at Breast Cancer Diagnosis

A 2017 study found that among BRCA2 carriers diagnosed with breast cancer before age 50, oophorectomy was associated with 82% breast cancer risk reduction (HR 0.18; 95% CI 0.05-0.63), though this benefit was not significant in BRCA1 carriers in this specific analysis 1

For Women WITHOUT BRCA Mutations

Average-Risk Women

The evidence is much weaker and more concerning for women at average risk:

• A 2020 study of 49,215 women undergoing hysterectomy for benign indications found only a 14% lower breast cancer risk with concurrent oophorectomy (HR 0.86; 95% CI 0.75-0.98) 5
• However, all-cause mortality was significantly higher in women with oophorectomy (64.4% vs 35.6%) 5
• This suggests that for average-risk women, the modest breast cancer risk reduction is outweighed by increased mortality from other causes (likely cardiovascular disease, osteoporosis complications) 5

Women with Family History (Non-BRCA)

• A 2004 study of 680 women with family history who underwent oophorectomy showed breast cancer rates one-half to one-fourth of expected rates 6
• The protective effect was stronger in women who were premenopausal and under age 50 at surgery 6

Clinical Algorithm for Decision-Making

Step 1: Determine BRCA Mutation Status

• If BRCA1/2 positive: RRSO provides substantial breast cancer risk reduction and mortality benefit
• If BRCA negative or unknown: Benefits are uncertain and may be outweighed by harms

Step 2: Consider Age

• Age ≤40 years (BRCA1): Maximum breast cancer risk reduction (64%)
• Age 41-50 years (BRCA1): Moderate benefit (50% reduction)
• Age >50-51 years: Minimal to no breast cancer risk reduction benefit

Step 3: Weigh Additional Factors

• RRSO reduces ovarian cancer risk by 80-90% in BRCA carriers, which may be the primary indication 2, 3
• Hormone replacement therapy (HRT) until age 50-51 does not negate breast cancer risk reduction and is recommended to mitigate cardiovascular and bone health risks 2
• Salpingectomy alone (removing tubes but keeping ovaries) does NOT provide the breast cancer risk reduction that oophorectomy provides 1, 3

Critical Caveats and Common Pitfalls

Avoid These Mistakes:

1. Don't assume benefit applies to all women—the evidence is specific to BRCA mutation carriers, particularly BRCA1 1

2. Don't perform RRSO after natural menopause age expecting breast cancer benefit—surgery after age 50-51 shows minimal to no breast cancer risk reduction 1

3. Don't withhold HRT in BRCA carriers after RRSO—short-term HRT until natural menopause age does not eliminate the breast cancer protective effect and is important for bone and cardiovascular health 2

4. Don't recommend salpingectomy alone as equivalent to RRSO for breast cancer risk reduction—removing only the tubes without the ovaries does not provide the hormonal changes needed for breast cancer risk reduction 1, 3

5. Don't ignore the quality-of-life trade-offs in average-risk women—the increased all-cause mortality in non-BRCA carriers suggests net harm 5

Mechanism of Action

The breast cancer risk reduction is attributed to decreased ovarian hormone exposure after surgical removal of the ovaries, which is why timing before natural menopause matters and why the effect is lost when surgery occurs after age 50 1

Ongoing Surveillance Requirements

Even after RRSO, BRCA carriers must continue:

• Annual breast MRI starting age 25 7
• Annual mammography starting age 30 7
• Clinical breast examination every 6-12 months 7

The residual breast cancer risk remains elevated compared to the general population even after RRSO 1