When a person is diagnosed with breast cancer, surgery can be their first treatment. Other times, their clinician will prescribe chemotherapy before surgery, called neoadjuvant chemotherapy. In both cases, for patients with clinically negative nodes at presentation, surgeons will determine at the time of surgery how far the cancer has spread by removing and examining several lymph nodes, called “sentinel lymph nodes” from the underarm area.

Lymph nodes are an important part of the immune system. People who have had lymph nodes removed, or whose lymph nodes are damaged, are at increased risk of developing a condition where lymph pools in a limb and causes swelling, called lymphedema. Lymphedema is life altering and treatment is complex, so surgeons try to remove as few lymph nodes as possible to minimize the risk of lymphedema development.

Recent Mayo Clinic research, published in Annals of Surgical Oncology, suggests that up to three sentinel lymph nodes is the maximum number surgeons need to remove for a specific group of patients – those who were clinically node-negative and treated with neoadjuvant chemotherapy prior to surgery.

"Our study applies to patients who have no lymph node disease identified on imaging or physical exam [called clinically node-negative] prior to receiving neoadjuvant chemotherapy,” says Brittany Murphy, M.D., study lead author. Dr. Murphy was a general surgery resident at Mayo Clinic from 2013-2019. She is currently a breast surgical oncologist at Banner MD Anderson Cancer Center, and maintains a research affiliation at Mayo.

When Dr. Murphy, or another surgeon, removes a breast tumor, she will also remove several lymph nodes draining lymph from the region of tumor. These are examined for cancerous cells to see if cancer has spread to the axilla (armpit).

"Being clinically node-negative does not mean the nodes are free of microscopic disease," says Dr. Murphy. "So we remove sentinel lymph nodes – those that drain the breast first – and a lab examination tells us whether the cancer has spread into the axilla."

Cancer in the lymph nodes in the axilla will require a modified treatment plan, typically including additional surgery and possibly radiation therapy, says Dr. Murphy. 

The number of sentinel lymph nodes removed during breast cancer surgeries can vary significantly and on occasion can be as high as 10+. Studies have shown that if a sentinel lymph node is positive in patients undergoing surgery as their first line of treatment, the positive node will most likely be identified within the first four sentinel lymph nodes removed.

"A patient’s quality of life is reduced by the development of lymphedema, so we want to do everything we can to decrease the risk of development," says Dr. Murphy. "We wanted to find the finite number that would help us provide better care for patients who receive chemotherapy before surgery. We don't want to remove a dozen lymph nodes if we can gain the same information from removing far fewer."

Evidence-based transformation through research

Dr. Murphy and her colleagues examined the records of 440 patients diagnosed with clinical node-negative invasive breast cancer between 2008 and 2018. These patients received neoadjuvant chemotherapy and underwent sentinel lymph node surgery, at Mayo Clinic in Rochester, Minn. Among these surgeries, the researchers report that if a sentinel lymph node had cancer, it was most commonly identified in the first one removed. They identified the cancer by the third lymph node removed in the all cases. The authors conclude that once three sentinel lymph nodes have been removed and checked, any additional removals are not necessary for diagnosis

Pending larger studies and further validation, this information could guide surgeons to cap the number of sentinel lymph nodes they remove, thereby reducing their patients' risk of lymphedema and related poor outcomes.

This study adds to the body of knowledge that enables Mayo Clinic patients to receive the best possible care. Breast cancer patients – truly all patients – benefit from the partnership between research and practice at Mayo Clinic, because it embeds clinical evolution in everyday care.

"We have many projects looking to evaluate the breast cancer practice at Mayo," says Judy Boughey, M.D., Mayo Clinic breast surgeon, study senior author, and vice chair for research, Department of Surgery. "We want to ensure continuous improvement and transformation of the practice, while ensuring the value of the care we provide."

Although professional society guidelines exist regarding the use of sentinel lymph node surgery, to date no guidelines specify the number to remove.

"If future guidelines are revised and updated it would be reasonable to include the findings from our paper to guide number of lymph nodes removed," says Dr. Boughey. "Additional validation in a larger sample size would also be warranted before making this an absolute recommendation."

Meanwhile, she says, "These findings can help guide intraoperative decision making for surgeons everywhere." Dr. Boughey is also the W.H. Odell Professor in Individualized Medicine, and program director for the Multidisciplinary Breast Surgery Fellowship in the Mayo Clinic College of Medicine and Science.

Dr. Murphy says it will certainly guide her practice. She uses what she learned at Mayo Clinic every day, including referencing the various research studies she co-authored with Dr. Boughey. She credits Dr. Boughey's mentorship as key to her to path to becoming a breast surgical oncologist.

This is not an uncommon story among surgeons, or anywhere at Mayo Clinic, where the third aspect of Mayo Clinic’s expert care is education.

The breast surgeons are all actively involved with multiple mentored research projects and enjoy continuously evaluating, improving and furthering the clinical practice," says Dr. Boughey.

For herself and her colleagues, she says, "We enjoy working with young, energetic dedicated individuals to learn about research methodology, presentation and publication."

This research and publication was made possible by the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery. Embedded in the practice, the center seeks to discover new ways to improve health; translate those discoveries into evidence-based, actionable treatments, processes and procedures; and apply this new knowledge to improve care for Mayo Clinic patients and people everywhere. 

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Related link: Sentinel Lymph Node Working Group

The Mayo Clinic College of Medicine and Science includes five schools:

• Mayo Clinic Alix School of Medicine
• Mayo Clinic School of Graduate Medical Education
• Mayo Clinic School of Health Sciences
• Mayo Clinic Graduate School of Biomedical Sciences
• Mayo Clinic School of Continuous Professional Development

Tags: breast cancer, Brittany Murphy, cancer research, Center for the Science of Health Care Delivery, chemotherapy, Findings, Judy Boughey, lymphatic system, lymphedema, Mayo Clinic College of Medicine and Science, News, oncology, Progress Updates, residency program