Why is a bilateral mastectomy (double mastectomy) performed when only one breast contains malignant tissue (cancer)?

From the Guidelines

A double mastectomy is recommended for patients with a high risk of developing cancer in the unaffected breast, such as those with BRCA1 or BRCA2 gene mutations, as it reduces the risk of subsequent breast cancer by 90%–95%. This approach is typically done for preventive reasons, and some patients choose this option to reduce anxiety about future cancer development and to avoid ongoing surveillance with mammograms and MRIs. According to the most recent guidelines, risk-reducing surgery, including prophylactic bilateral mastectomy and reconstruction, may be offered to women at very high risk, such as BRCA1 or BRCA2 mutation carriers 1. The procedure involves removing both breasts during the same surgery, with the option for immediate or delayed reconstruction. Recovery typically takes 4-6 weeks, with restrictions on lifting and physical activity.

The decision to undergo a double mastectomy should always be made after thorough discussion with a surgical oncologist, considering both medical factors and personal preferences, as it's a significant procedure with permanent body changes. It's essential to note that non-high-risk patients who opt for bilateral mastectomy rather than the preferred breast conservation should be counselled that survival outcomes in patients with early-stage breast cancer treated with breast-conserving surgery might be even better (and certainly not worse) than those treated with mastectomy 1. Additionally, the lifetime risk of breast cancer in a BRCA1 mutation carrier varies between 65% and 90%, with a 10-year actuarial risk of contralateral breast cancer ranging from 25% to 31% 1.

Key points to consider when deciding on a double mastectomy include:

• High risk of developing cancer in the unaffected breast, such as BRCA1 or BRCA2 gene mutations
• Reduction of anxiety about future cancer development
• Avoidance of ongoing surveillance with mammograms and MRIs
• Symmetry in appearance after reconstruction
• Thorough discussion with a surgical oncologist, considering both medical factors and personal preferences.

From the Research

Reasons for Double Mastectomy

• A double mastectomy may be performed even if only one breast has cancer tissue in women with a high risk of breast cancer, such as those with BRCA1 or BRCA2 mutations 2.
• The goal of this procedure is to reduce the risk of developing breast cancer in the future, as women with these mutations have a significantly increased risk of breast cancer 2.
• Studies have shown that bilateral prophylactic mastectomy can reduce the risk of breast cancer by 90% or more in patients with BRCA mutations 2.

Considerations for Double Mastectomy

• The decision to undergo a double mastectomy should be made on a case-by-case basis, taking into account the individual's risk factors, medical history, and personal preferences 2.
• Women who undergo double mastectomy may still be at risk of developing breast cancer, although the risk is significantly reduced 3.
• The procedure can also have psychological and physical effects, such as loss of sensitivity and body image issues 2.

Alternative Options

• Alternative options for reducing breast cancer risk include surveillance with mammography and magnetic resonance imaging, chemoprevention with tamoxifen or raloxifene, and risk-reducing salpingo-oophorectomy 4, 2, 5.
• These options may be considered for women who are at high risk of breast cancer but do not wish to undergo a double mastectomy 4, 2, 5.