TORONTO – July 25, 2024 – A groundbreaking study conducted by a team at Women’s College Hospital Research and Innovation Institute, challenges the perceived benefits of bilateral mastectomy for patients with unilateral breast cancer. The research, published in JAMA Oncology, followed 108,084 breast cancer patients over 20 years. It found that while bilateral mastectomy significantly reduces the risk of contralateral breast cancer, it does not lower the risk of breast cancer mortality compared to unilateral mastectomy or lumpectomy.
The findings raise several fundamental questions about the nature of breast cancer with potential implications for the screening, treatment, and survivorship of the disease.
Key Findings:
- The study involved three equally matched groups of breast cancer patients (n = 36,028 each) who underwent either unilateral mastectomy, lumpectomy, or bilateral mastectomy.
- Bilateral mastectomy reduced the risk of contralateral breast cancer by 88 per cent but showed no significant impact on breast cancer mortality.
- The 20-year cumulative risk of contralateral breast cancer was 6.9 per cent for patients undergoing lumpectomy or unilateral mastectomy and only 0.7 per cent for those who had bilateral mastectomy.
- Breast cancer mortality after 20 years was nearly identical across all three groups: 16.3 per cent for lumpectomy, 16.7 per cent for unilateral mastectomy, and 16.7 percent for bilateral mastectomy.
Study Significance: This comprehensive study raises important questions about the metastatic potential of a new contralateral breast cancer and the true benefits of bilateral mastectomy for unilateral breast cancer patients. Despite the reduced incidence of contralateral cancer, the similar mortality rates suggest that bilateral mastectomy may not offer the survival benefit many patients and clinicians expect.
“Traditionally, it is assumed that a contralateral breast cancer is a new primary cancer with the potential to metastasize and thus impact overall survival negatively,” says Vasily Giannakeas, PhD, a researcher at the Women’s College Hospital Research and Innovation Institute and lead author of the paper. “However, the similar mortality rates across all surgical groups suggest that the occurrence of contralateral cancer may be more of a marker of an already existing higher risk of mortality rather than an independent cancer event that drives an increase in mortality.”
The study also raises important questions about the effectiveness of current screening strategies and adjuvant therapies, such as chemotherapy, in the treatment of contralateral breast cancer.
“About one-third of patients with contralateral breast cancer are treated with chemotherapy, “says Giannakeas. However, it now seems we are trying to treat the first cancer and chemotherapy may not be as effective. These are compelling questions that we hope to address in future studies.”
“For now, this research’s findings are valuable to the patient and their physician as they look to decide on surgical options to treat breast cancer.”
For media inquiries, please contact:
Maria Madden, Manager, Public Affairs, Women’s College Hospital, maria.madden@wchospital.ca.
About Women’s College Hospital
For more than 100 years Women’s College Hospital (WCH) has been developing revolutionary advances in healthcare. Today, WCH is a world leader in health equity and Canada’s leading academic ambulatory hospital. It focuses on delivering innovative solutions that address Canada’s most pressing issues related to population health, patient experience and system costs. A multidisciplinary research institute, the Women’s College Research and Innovation Institute is one of only a few hospital-based research institutes worldwide to focus on health equity, leading innovative, high-impact health research that changes practice, changes policy, and changes lives. www.womenscollegehospital.ca