Study Questions Life-Saving Benefits of Double Mastectomy

A recent large-scale study has raised important questions about the effectiveness of bilateral mastectomy in reducing breast cancer mortality for women with cancer in one breast. The study followed 661,270 women over 20 years and found that while having both breasts removed significantly reduced the risk of developing cancer in the other breast, it did not improve survival rates compared to other surgical options.

Study Design and Participants

Researchers used data from the SEER Program registry, focusing on women diagnosed with early to mid-stage unilateral breast cancer between 2000 and 2019. The study divided these women into three groups based on their surgery type: lumpectomy, unilateral mastectomy, and bilateral mastectomy. Each group included 36,028 women, and they were followed for 20 years to track the incidence of cancer in the opposite breast and overall breast cancer mortality.

Key Findings

During the follow-up period, fewer women in the bilateral mastectomy group developed cancer in the opposite breast (97 cases) compared to the lumpectomy (766 cases) and unilateral mastectomy (728 cases) groups. However, the 20-year mortality rates from breast cancer were similar across all three groups: 16.3% for lumpectomy, 16.7% for unilateral mastectomy, and 16.7% for bilateral mastectomy.

Implications

This study highlights that while bilateral mastectomy can prevent cancer in the opposite breast, it doesn't necessarily help women live longer. This suggests that developing cancer in the other breast may not be a major factor in breast cancer deaths, calling into question the need for bilateral mastectomy solely to prevent a second cancer.

Risk of Contralateral Breast Cancer

The chance of developing cancer in the other breast over 20 years was 6.9% for those who had lumpectomy or unilateral mastectomy. The risk was slightly higher for patients with a non-invasive type of cancer called DCIS (8.2%) compared to those with invasive cancer (6.8%). It was also higher for patients with lobular cancer (7.1%) and those with mixed cancer types (8.0%).

Breast Cancer Mortality and Contralateral Cancer

A key finding was the fourfold increase in breast cancer mortality for women who developed cancer in the other breast. The hazard ratio for dying from breast cancer after experiencing this was 4.00. However, despite this increased risk, the overall mortality rates were similar between the different surgical groups.

Study Limitations

The study noted several limitations, such as not having data on the use of hormone therapy, family history, BRCA gene mutations, and cancer screening records. These factors could affect the risk of cancer in the other breast and overall mortality. Additionally, the study focused on a specific patient profile, which may limit how applicable the findings are to all breast cancer patients.

Conclusion

The findings suggest that women with cancer in one breast who choose bilateral mastectomy to reduce the risk of a second cancer may not see a survival benefit. This study underscores the importance of personalized advice and informed decision-making for breast cancer patients considering this surgery. Women should know that while bilateral mastectomy reduces the risk of cancer in the other breast, it doesn't necessarily improve long-term survival.