The false-negative rate of sentinel lymph node results was almost 13% after neoadjuvant chemotherapy, in a study of women initially presenting with biopsy-proven node-positive breast cancer, which is above the acceptable threshold, a study has shown.
Considering the threshold for a false-negative rate is 10%, "changes in approach and patient selection that result in greater sensitivity would be necessary" to support the use of sentinel lymph node (SLN) surgery "as an alternative" to axillary lymph node dissection in this population of patients with breast cancer, concluded Dr. Judy Boughey of the department of surgery, Mayo Clinic, Rochester, Minn., and her associates in the Alliance for Clinical Trials in Oncology.
Dr. Judy C. Boughey
The investigators also found that false-negative SLN biopsy results were significantly lower when two mapping agents were used; the false-negative rate was also significantly lower when at least three sentinel lymph nodes were sampled. The results of the study were presented at the annual clinical congress of the American Congress of Surgeons and simultaneously published online on Oct. 7, 2013, in JAMA (doi:10.1001/jama.2013.278932).
The phase II study addressed the false-negative rate of SLN biopsy after neoadjuvant chemotherapy, in women who initially presented with pathologically confirmed node-positive disease. The study enrolled 701 women from July 2009 to June 2011, at 136 institutions. The women had clinical stage T0 through T4, N1 through N2, M0 breast cancer; most (663) had cN1 disease (disease in movable axillary lymph nodes) and 38 had cN2 disease (disease in fixed or matted axillary lymph nodes). After chemotherapy was completed, the patients had surgery, involving SLN biopsy and axillary lymph node dissection.
Of the 701 women, 687 underwent both SLN biopsy and axillary lymph node dissection, 2 had only SLN biopsy, and 12 had axillary lymph node dissection only. Most of the 689 women who underwent SLN biopsy had the procedure performed with blue dye and radiolabeled colloid (79%), 116 (16.8%) had radiolabeled colloid only, and 28 (4.1%) had blue dye only.
Of the 689 women who had SLN biopsy, at least one SLN was detected in 639 (almost 93%). Among the 651 women with cN1 disease, at least one SLN was detected in 605 women (93%); and among the 38 women with cN2 disease, at least one SNL was detected in 34 (89.5%).
In 525 of the patients with cN1 disease, at least two SLNs were excised and axillary lymph node dissection was completed. There was no residual node disease found in 215 of these patients, for a nodal pathologic complete response rate of 41%.
Of the remaining 310 patients, nodal disease was found in the sentinel lymph nodes in 108 patients (20.6%), and in both axillary and sentinel nodes in 163 patients (31.1%).
Residual node disease was found in the axillary lymph nodes of only 39 (7.4%) of the patients. Therefore, the results of the SLN biopsy results were false negative in 39 of the 310 patients, for a false negative rate of 12.6%.
While the study results "suggest that surgeons cannot reliably detect all axillary lymph node metastases in patients with cN1 breast cancer following chemotherapy" with SLN procedures, "we did identify important factors influencing the likelihood of a false-negative SLN," the authors said. The false-negative rate for the SLN biopsy results was significantly decreased when both blue dye and radiolabeled colloid were used as mapping agents, and when at least three sentinel lymph nodes were biopsied.
When both blue dye and radiolabeled colloid were used, the false-negative rate was 10.8%, compared with 20.3% when only one agent was used. "Using two mapping agents with different molecule sizes and transit times is an important surgical standard that should be adhered to for SLN surgery after chemotherapy," they said, noting that after chemotherapy, "the axilla often has more fibrosis, making evaluation of lymphatic drainage and surgical dissection more challenging."
And when at least three SLNs were examined, the false negative rate was 9.1%, compared with 21.1% when two were sampled. "As the accuracy of any sampling test is dependent on the amount of material sampled, these results are not surprising," they said, noting that this has been found in other studies.
SLN is less invasive than axillary dissection and is considered a reliable way to check for axillary nodal disease in women who present with node-negative disease, but the use of SLN biopsy after neoadjuvant chemotherapy in women with cN1 disease "has been questioned," because the false-negative rate for this approach in this population has ranged from 7% to 25% in small studies, the only data available on this approach, according to the authors.