Predictive Factors for Positive Non-Sentinel Nodes Following a Positive Sentinel Node Biopsy: NSABP B-32.

Abstract

Abstract Background: Following a positive sentinel node biopsy (SNB), current guidelines recommend an axillary dissection (AD) regardless of SN metastatic tumor size. In the majority of clinically node negative patients the risk for positive non-sentinel axillary nodes (NSN) is low. Predictive factors for positive NSNs following a positive SNB are analyzed in NSABP B-32 with inclusion of SN metastatic tumor size.Materials and Methods: After stratification, women with operable invasive breast cancer and clinically negative nodes were randomized to Sentinel Node Resection (SNR) with immediate conventional Axillary Dissection (AD) [Group 1] or to SNR without AD [Group 2]. Group 2 patients with positive SNs underwent AD. A multivariate analysis of SN positive patients from both groups for whom both a SNR and an AD had been performed was used to assess the need for AD following SNB. Nodes were classified as either SNs or NSNs, defined as all axillary dissection nodes plus any intramammary or other nodes that were not resected as SNs.Results: Between May 1999 and February 2004, 5,611 patients were entered into NSABP Protocol B-32. There were a total of 1,361 SN positive patients with AD from both groups. Data from 1,166 patients were available for multivariate analysis which included SN metastatic tumor size in 735 patients: 424 patients with macrometastaes (>2 mm) and 311 with micrometastases (<2 mm). In 626 patients SN metastatic size was unknown.In patients with positive SNB, results from the final multivariate model based on 653 patients with known covariate values indicated clinical tumor size was a significant predictor for positive NSN (p=0.044, OR: 1.17). Lymphovascular invasion was a significant predictor for positive NSN (p=0.0004, OR: 1.85). SN metastatic tumor size (Macro vs Micro) was a highly significant predictor for positive NSN (p<0.0001, OR: 3.42). Age at study entry, treatment type, proposed type of surgery, HER-2 status, and location of tumor were not significant multivariate predictors for positive NSN. Predictive modeling for positive NSN probability will be presented.Conclusion: Completion AD following a positive SNB, although helpful in prognosis and treatment planning, may not be required in patients with small tumors, absence of lymphovascular invasion, and micrometastases. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 301.