Sentinel lymph node biopsy for breast cancer: Impact of the number of sentinel nodes removed on the false-negative rate

BACKGROUND: Numerous studies have demonstrated that sentinel lymph node (SL N) biopsy can accurately determine axillary nodal status for breast cancer, but unacceptably high false negative rates have also been reported. Attent ion has been focused on factors associated with improved accuracy. We have previously shown that injection of blue dye in combination with radioactive colloid reduces the false negative rate compared with injection of blue dy e alone. We hypothesized that this may be from the increased ability to ide ntify multiple sentinel nodes. The purpose of this analysis was to determin e whether removal of multiple SLNs results in a lower false negative rate. STUDY DESIGN: The University of Louisville Breast Cancer Sentinel Lymph Nod e Study is a prospective multiinstitutional study. Patients with clinical s tage T1-2, NO breast cancer were eligible for enrollment. All patients unde rwent SLN biopsy using blue dye alone, radioactive colloid alone, or both a gents in combination, followed by completion level I and II axillary dissec tion. RESULTS: A total of 1,436 patients were enrolled in the study from August 1 997 to February 2000, SLNs were identified in 1,287 patients (90%), with an overall false negative rate of 8.3%. A single SLN was removed in 537 patie nts. Multiple SLNs were removed in 750 patients. The false negative rates w ere 14.3% and 4.3% for patients with a single sentinel node versus multiple sentinel nodes removed, respectively (p = 0.0004, chi-square). Logistic re gression analysis revealed that use of blue dye injection alone was the onl y factor independently associated with identification of a single SLN (p<0. 0001), and patient age, tumor size, tumor location, surgeon's previous expe rience, and type of operation were not significant. CONCLUSIONS: The ability to identify multiple sentinel nodes, when they exi st, improves the diagnostic accuracy of SLN biopsy. Injection of radioactiv e colloid in combination with blue dye improves the ability to identify mul tiple sentinel nodes compared with the use of blue dye alone. (J Am Coll Su rg 2001;192:684-691. (C) 2001 by the American College of Surgeons).