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Importance: Sentinel lymph node (SLN) surgery provides reliable nodal staging information with less morbidity than axillary lymph node dissection (ALND) for patients with clinically node-negative (cN0) breast cancer. The application of SLN surgery for staging the axilla following chemotherapy for women who initially had node-positive cN1 breast cancer is unclear because of high false-negative results reported in previous studies., Objective: To determine the false-negative rate (FNR) for SLN surgery following chemotherapy in women initially presenting with biopsy-proven cN1 breast cancer., Design, Setting, and Patients: The American College of Surgeons Oncology Group (ACOSOG) Z1071 trial enrolled women from 136 institutions from July 2009 to June 2011 who had clinical T0 through T4, N1 through N2, M0 breast cancer and received neoadjuvant chemotherapy. Following chemotherapy, patients underwent both SLN surgery and ALND. Sentinel lymph node surgery using both blue dye (isosulfan blue or methylene blue) and a radiolabeled colloid mapping agent was encouraged., Main Outcomes and Measures: The primary end point was the FNR of SLN surgery after chemotherapy in women who presented with cN1 disease. We evaluated the likelihood that the FNR in patients with 2 or more SLNs examined was greater than 10%, the rate expected for women undergoing SLN surgery who present with cN0 disease., Results: Seven hundred fifty-six women were enrolled in the study. Of 663 evaluable patients with cN1 disease, 649 underwent chemotherapy followed by both SLN surgery and ALND. An SLN could not be identified in 46 patients (7.1%). Only 1 SLN was excised in 78 patients (12.0%). Of the remaining 525 patients with 2 or more SLNs removed, no cancer was identified in the axillary lymph nodes of 215 patients, yielding a pathological complete nodal response of 41.0% (95% CI, 36.7%-45.3%). In 39 patients, cancer was not identified in the SLNs but was found in lymph nodes obtained with ALND, resulting in an FNR of 12.6% (90% Bayesian credible interval, 9.85%-16.05%)., Conclusions and Relevance: Among women with cN1 breast cancer receiving neoadjuvant chemotherapy who had 2 or more SLNs examined, the FNR was not found to be 10% or less. 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 ALND., Trial Registration: clinicaltrials.gov Identifier: NCT00881361.

Context: Sentinel lymph node dissection (SLND) accurately identifies nodal metastasis of early breast cancer, but it is not clear whether further nodal dissection affects survival., Objective: To determine the effects of complete axillary lymph node dissection (ALND) on survival of patients with sentinel lymph node (SLN) metastasis of breast cancer., Design, Setting, and Patients: The American College of Surgeons Oncology Group Z0011 trial, a phase 3 noninferiority trial conducted at 115 sites and enrolling patients from May 1999 to December 2004. Patients were women with clinical T1-T2 invasive breast cancer, no palpable adenopathy, and 1 to 2 SLNs containing metastases identified by frozen section, touch preparation, or hematoxylin-eosin staining on permanent section. Targeted enrollment was 1900 women with final analysis after 500 deaths, but the trial closed early because mortality rate was lower than expected., Interventions: All patients underwent lumpectomy and tangential whole-breast irradiation. Those with SLN metastases identified by SLND were randomized to undergo ALND or no further axillary treatment. Those randomized to ALND underwent dissection of 10 or more nodes. Systemic therapy was at the discretion of the treating physician., Main Outcome Measures: Overall survival was the primary end point, with a noninferiority margin of a 1-sided hazard ratio of less than 1.3 indicating that SLND alone is noninferior to ALND. Disease-free survival was a secondary end point., Results: Clinical and tumor characteristics were similar between 445 patients randomized to ALND and 446 randomized to SLND alone. However, the median number of nodes removed was 17 with ALND and 2 with SLND alone. At a median follow-up of 6.3 years (last follow-up, March 4, 2010), 5-year overall survival was 91.8% (95% confidence interval [CI], 89.1%-94.5%) with ALND and 92.5% (95% CI, 90.0%-95.1%) with SLND alone; 5-year disease-free survival was 82.2% (95% CI, 78.3%-86.3%) with ALND and 83.9% (95% CI, 80.2%-87.9%) with SLND alone. The hazard ratio for treatment-related overall survival was 0.79 (90% CI, 0.56-1.11) without adjustment and 0.87 (90% CI, 0.62-1.23) after adjusting for age and adjuvant therapy., Conclusion: Among patients with limited SLN metastatic breast cancer treated with breast conservation and systemic therapy, the use of SLND alone compared with ALND did not result in inferior survival., Trial Registration: clinicaltrials.gov Identifier: NCT00003855.