Sentinel lymph node surgery performed after neoadjuvant chemotherapy in women presenting with node-positive disease could spare many patients with breast cancer needless axillary lymph node dissection, according to a study of the American College of Surgeons Oncology Group presented at the 2012 San Antonio Breast Cancer Symposium (ACOSOG Z1071).¹

“We showed that sentinel lymph node surgery correctly identified the nodal status in 91.2% of patients who were node-positive at presentation and who underwent neoadjuvant chemotherapy,” said Judy C. Boughey, MD, of the Mayo Clinic, Rochester, Minnesota.

Based on the factors that were shown to be associated with the lowest risk of false-negatives, Dr. Boughey said she would “feel safe incorporating sentinel node surgery in clinical practice in cases where patients have a good clinical response to chemotherapy, undergo sentinel node mapping with standardization of the technique, and have three or more sentinel nodes identified. I feel the false-negative rate is acceptable in that group.”

Study Questions and Details

Sentinel lymph node surgery is routinely used for patients initially diagnosed with node-negative disease. The study evaluated whether it could be safely used in patients with node-positive breast cancer who are treated with neoadjuvant chemotherapy, most of whom undergo axillary node dissection.

“The question is whether removal of the lymph nodes with an axillary dissection is needed, or whether less-invasive surgery would reliably identify patients who still have disease in the lymph nodes and which patients have converted to negative nodes,” she said. “Our hypothesis was that sentinel node surgery is an accurate method of axillary staging in these patients.”

The primary endpoint was the false-negative rate for sentinel node surgery in patients who had at least two sentinel nodes examined, the expectation being that the rate would be 10% or lower, she said.

Subset of Interest

The multicenter study included 756 patients with node-positive breast cancer who received neoadjuvant chemotherapy. Of these, 637 underwent both sentinel lymph node surgery and axillary dissection. Sentinel node surgery correctly identified the nodal status in 91.2% of patients, including 255 (40%) who were ultimately node-negative and 382 (60%) who had residual nodal disease—which was the subset of interest in the study.

Of these 382 patients, axillary dissection confirmed that 326 were indeed sentinel node–positive, while 56 patients were sentinel node–negative but node-positive according to the axillary dissection. Sentinel node surgery, therefore, correctly identified the nodal status in 91.2% of patients.

Among the 310 patients fitting the criteria for the primary endpoint—those with clinical N1 disease who had at least two sentinel nodes examined—39 had negative sentinel nodes, yielding a false-negative rate of 12.6% (95% probability = 9.4%–16.7%), Dr. Boughey reported.

Lower False-negative Rates

The false-negative rate was lower when both blue dye and radiolabeled colloid were used (10.8%; P = .046), and when at least three sentinel nodes were examined (9.1%; P = .004). The false-negative rate was 21.1% with two nodes examined, 9.0% with three nodes, 6.7% with four nodes, and 11.0% with five or more nodes examined, she said.

Of the 78 patients with clinical N1 disease who had only one sentinel node examined, 24 had no residual nodal disease, while 17 of the 54 with residual nodal disease had false-negative sentinel node findings, producing a false-negative rate of 31.5% in this group, she added.

When histologic changes consistent with therapy effect were present, as was the case for 35.5% of patients, the false-negative rate was 10.8%. When therapy effect was not documented, the rate was 13.5%. When a clip was placed in positive lymph nodes at diagnosis, as was done for 32.8% of patients, the false-negative rate dropped to 7.4% among patients where the clip was found in the sentinel lymph node(s). There was no statistically significant difference according to clinical T stage. For the 34 patients with clinical N2 disease, there were no false-negatives, she reported.

“We conclude that sentinel lymph node surgery is a useful tool for the detection of residual nodal disease in women with node-positive disease receiving neoadjuvant chemotherapy, but surgical technique is important for minimizing the false-negative rate,” Dr. Boughey said. “Use of a dual tracer and resection of at least two sentinel nodes is important. Clip placement may help improve the accuracy as well as pathologic review of the sentinel nodes for treatment effect.” ■

Disclosure: Dr. Boughey reported no potential conflicts of interest.

Reference

1. Boughey JC, Suman VJ, Mittendorf EA, et al: The role of sentinel lymph node surgery in patients presenting with node positive breast cancer (T0-T4, N1-2) who receive neoadjuvant chemotherapy: Results from the ACOSOG Z1071 trial. 2012 San Antonio Breast Cancer Symposium. Abstract S2-1. Presented December 5, 2012.