Sentinel lymph node surgery correctly identified nodal status after treatment with neoadjuvant chemotherapy in 84% of patients with node-positive breast cancer. Thus, sentinel lymph node (SLN) surgery could provide a less invasive option for nodal staging in this population.

Most women with breast cancer that has spread to their lymph nodes undergo axillary lymph node dissection (ALND). However, treatment with chemotherapy before surgery, which is neoadjuvant chemotherapy, can eradicate disease in the lymph nodes of some patients, converting them to node-negative status.

For patients with initially diagnosed node-negative disease, SLN surgery is routinely used. This study investigated the feasibility of using SLN surgery for patients with node-positive breast cancer who undergo neoadjuvant chemotherapy.

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The research project was led by Judy C. Boughey, MD, of the Mayo Clinic in Rochester, Minnesota, who explained in regards to node-positive breast cancer, “the question arises as to whether removal of the lymph nodes with an ALND is needed, or whether less invasive surgery, with a sampling of the nodes by SLN surgery alone, would reliably identify which patients still have disease in the lymph nodes and which patients have negative lymph nodes.”

The investigators conducted a multicenter study of 756 women with node-positive breast cancer who received neoadjuvant chemotherapy and underwent surgery. Of these patients, 637 underwent both SLN surgery with identification and removal of the sentinel nodes under the arm and ALND to remove most of the lymph nodes in the axilla. Nodal status was correctly identified by SLN surgery in 91% of the patients, including 255 patients now with node-negative breast cancer and 326 patients with continuing node-positive disease.

The research team also found that 40% of the patients for which an SLN could be identified had a complete pathological response in the lymph nodes, meaning eradication of active disease in the lymph nodes.

“If SLN surgery is accurate for evaluating the lymph nodes after neoadjuvant chemotherapy, it potentially could allow patients to avoid ALND and undergo SLN for axillary staging and only require an ALND if the SLN is positive,” Boughey said. She noted a false-negative rate of 12.6%.

“This rate is lower with use of dual tracer (blue dye and radiolabelled colloid) to identify the SLN, and the false-negative rate is lower the more SLNs are removed. Therefore, technical factors are important to minimize incorrect nodal staging,” she said.

This study by the American College of Surgeons Oncology Group (ACOSOG) was presented at the CTRC-AACR San Antonio Breast Cancer Symposium, held December 4-8, 2012.