Challenges of Contralateral Breast Cancer & Surgical Interventions

Breast Cancer: Breast CancerThe decision to undergo bilateral mastectomy for unilateral breast cancer has been a topic of debate across oncology, and patients and physicians alike trying to determine the potential benefits and risks. Recently, a study published in JAMA Oncology shed new light on this complex relationship between bilateral mastectomy, contralateral breast cancer, and mortality rates in breast cancer patients (2024; doi:10.1001/jamaoncol.2024.2212). The research, led by Vasily Giannakeas, PhD, MPH, a scientist and epidemiologist at the Women's College Hospital Research and Innovation Institute in Toronto, Canada, provided several insights that challenge the current understanding of breast cancer progression and treatment strategies. His team analyzed data from 661,270 women with breast cancer over 20 years, revealing that, while bilateral mastectomy significantly reduced the risk of contralateral breast cancer, it did not improve overall survival rates compared to less invasive surgical options. This finding has important long-term implications for patient care and treatment decision-making in breast cancer management. “Our study adds to the body of evidence showing that bilateral mastectomy in breast cancer patients significantly reduces the risk of contralateral cancer, but does not improve survival,” Giannakeas explained. “This finding aligns with current guidelines, which generally recommend breast-conserving surgery with radiotherapy for women with Stage 0 to Stage III unilateral breast cancer.” Contralateral Cancer Risk & Mortality One of the most intriguing aspects of the study is the apparent paradox that it reveals. The researchers found that developing contralateral breast cancer increased the mortality rate by fourfold. However, preventing it through bilateral mastectomy did not improve overall survival rates. This information calls into question the conventional understanding of contralateral breast cancer and its role in patient outcomes. “As researchers, we were interested in understanding the natural history of breast cancer in these patients,” Giannakeas said. “We have three major findings that, when combined, challenge our current view of contralateral breast cancer.” From these findings, the study also demonstrated that the 20-year risk of contralateral breast cancer was approximately 7 percent in patients who underwent lumpectomy or unilateral mastectomy. This is compared to just 0.7 percent of those who had bilateral mastectomy. Further, patients diagnosed with contralateral breast cancer experienced a fourfold increase in the rate of breast cancer death compared to those without contralateral cancer. However, long-term breast cancer survival was similar across all surgical groups, with 20-year survival rates of approximately 83 percent regardless of the type of surgery performed. Rethinking Contralateral Breast Cancer Above all, the findings of this study raise pivotal questions about the nature of contralateral breast cancer and its relationship to metastasis. Stemming from their research, Giannakeas and his team proposed a new theory that addresses contralateral breast cancer as a new primary cancer with metastatic potential. “Our current theory is that contralateral breast cancer is a marker of breast cancer mortality but does not cause an increase in mortality,” Giannakeas shared. “That is to say that aggressive cancer cells have already spread to the lung, liver, brain, or bone before the contralateral breast cancer is diagnosed, and the contralateral cancer is a sign that this spread has occurred.” He explained that this perspective aligns with established phenomena observed in other aspects of breast cancer progression, such as ipsilateral recurrence and lymph node involvement. In both cases, these events are markers of increased mortality risk, but preventing them does not necessarily lead to improved survival outcomes. Decision-Making Takeaways Giannakeas added that the study's findings have significant implications for breast cancer treatment strategies and patient decision-making. While the results support current guidelines that generally recommend breast-conserving surgery with radiotherapy for women with Stage 0-III unilateral breast cancer, they also provide “more precise estimates of long-term risks and outcomes associated with different surgical approaches,” according to the authors. “We hope our work will provide patients and clinicians with accurate estimates of [the] risk of contralateral breast cancer and survival, and aid in the decision-making process when a patient is diagnosed with unilateral breast cancer,” Giannakeas noted. Another takeaway from the research is that it suggests the choice of surgical intervention should be based on factors beyond just the prevention of contralateral breast cancer, as this prevention alone may not translate to improved survival outcomes. However, it's important to note that the study did identify one subgroup that might benefit more from bilateral mastectomy. According to Giannakeas, patients with lobular breast cancer showed a 20 percent reduction in the breast cancer mortality rate with bilateral mastectomy compared to lumpectomy. This particular finding highlights the importance of considering individual patient characteristics and tumor types when making treatment decisions. Screening & Treatment A point of consideration drawn from the study's findings is that it raises questions about the effectiveness of current screening and treatment approaches for contralateral breast cancer. If contralateral breast cancer is a marker of metastasis rather than a cause of increased mortality, it may necessitate a reevaluation of current practices. “If contralateral breast cancer is merely a marker for metastasis, routine screening for contralateral breast cancer may not be effective at reducing mortality,” Giannakeas stressed. “Moreover, about one-third of patients with contralateral breast cancer are treated with chemotherapy, and it may be appropriate to deescalate treatment in this context.” These insights could potentially lead to significant changes in how breast cancer is monitored and treated, particularly in patients who have already experienced primary breast cancer. However, Giannakeas and his team of researchers emphasize that further studies are needed to confirm these hypotheses and explore their clinical impact. Long-Term Outcomes One of the strengths of this study is its 20-year follow-up period, which provides valuable information about the long-term outcomes of breast cancer patients. The research team observed that the risk of contralateral cancer remains steady at approximately 0.4 percent per year after an ipsilateral breast cancer diagnosis in patients who choose lumpectomy or unilateral mastectomy. This long-term perspective is crucial for understanding the ongoing risks faced by breast cancer survivors. This is because it helps inform long-term care strategies. “The 20-year breast cancer mortality was 32 percent in patients who developed contralateral breast cancer compared to 16 percent in those who did not,” Giannakeas said. These findings reiterate the importance of long-term follow-up and risk assessment in breast cancer survivors, regardless of their initial surgical treatment choice. They also highlight the need for ongoing research into the factors that contribute to long-term survival and quality of life for breast cancer patients. Future Directions Moving forward, the study's findings open up several new directions for breast cancer research, particularly in early detection and treatment approaches. Giannakeas emphasizes the need for future studies to focus on detecting breast cancer cells at the earliest possible stage with the hope they might be more easily captured and treated. Ultimately, he believes exploring novel treatments such as cancer vaccines could be promising. That's why his research team also intends to investigate the metastatic potential of contralateral breast cancer and its implications for treatment strategies. Today, Giannakeas and his colleagues have become a part of a larger research effort challenging conventional wisdom in breast cancer research for the past decade. Their work, summarized in the book, A Fair Trial: The Foundations of Breast Cancer, raises fundamental questions about breast cancer biology and treatment. Looking ahead, they plan to assess the mechanisms of breast cancer metastasis and the relationship between primary and secondary tumors. Giannakeas shared that some of their most pressing questions involve when breast cancer metastasizes and the original source of metastasis. Answers to these questions could significantly advance their understanding of breast cancer progression. They could also lead to new therapeutic approaches that target the earliest stages of metastasis—helping to move the field of oncology forward. Lindsey Nolen is a contributing writer.

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