False negatives an issue in sentinel lymph node biopsy after chemo
Sentinel lymph node (SLN) surgery was associated with a false-negative rate (FNR) higher than a prespecified threshold in women who underwent chemotherapy after initially presenting with biopsy-proven breast cancer in movable axillary lymph nodes (cN1 disease).
“Given this FNR threshold, changes in approach and patient selection that result in greater sensitivity would be necessary to support the use of SLN surgery as an alternative to [axillary lymph node dissection, or ALND],” acknowledged Mayo Clinic (Rochester, Minnesota) breast surgeon Judy C. Boughey, MD, and co-investigators in their report in JAMA (2013;310:1455-1461).
Preoperative chemotherapy can eliminate breast cancer in the lymph nodes in some patients. Boughey and colleagues sought to evaluate whether SLN surgery could successfully identify whether cancer remained in the lymph nodes after chemotherapy. In patients with clinically node-negative (cN0) breast cancer, SLN surgery provides reliable nodal staging information, is less invasive than ALND, and is associated with less morbidity than is ALND. However, as Boughey's group explained, the use of SLN surgery for staging the axilla following chemotherapy for women who initially had node-positive cN1 breast cancer has been unclear due to high false-negative results seen in previous research.
Boughey's study focused on 756 women enrolled in the American College of Surgeons Oncology Group (ACOSOG) Z1071 trial. Of 663 evaluable patients with CN1 disease, 649 underwent chemotherapy followed by both SLN surgery and ALND.
SLN surgery correctly identified the presence or absence of cancer in 91% of patients, including 255 women with node-negative disease and 382 with continuing node-positive disease. In 46 women (7.1%), no SLN could be identified; in 78 women (12%), only one SLN was excised.
Of the remaining 525 patients, from whom two or more SLNs were removed, 215 (40.9%) had complete eradication of the cancer in the axillary lymph nodes. In 39 patients, cancer was not identified in the SLNs but was found in the lymph nodes obtained through ALND, resulting in an FNR of 12.6%. This exceeded the FNR of 10% expected for women undergoing SLN surgery who present with cN0 disease.
Boughey and coauthors noted that the FNR was significantly lower when dual tracers (blue dye and radiolabeled colloid) were used to identify the SLNs, and when more than two SLNs were removed.