Evaluation of the stage IB designation of the 7th edition of the AJCC Staging System.

Abstract

1130 Background: Recent data from large cooperative group trials have questioned the relevance of small volume metastases identified in the sentinel lymph nodes (SLN) of early stage breast cancer patients. The 7th ed. of the AJCC staging system differentiates node negative patients (stage IA) from those with micrometastases (stage IB) or macrometastases (stage II or III). This study was undertaken to determine the utility of the stage IB designation. Methods: Review of a prospectively maintained database identified 3474 patients who underwent SLN biopsy between 1993 and 2007. Clinicopathologic and outcomes data were recorded and patients staged according to the 7th ed. AJCC system. Recurrence-free (RFS), disease-specific (DSS) and overall survival (OS) were determined using the Kaplan-Meier method and compared using the log-rank test. Results: AJCC stage distribution included: 2246 (65%) stage IA, 207 (6%) stage IB, 685 (20%) stage IIA, 209 (6%) stage IIB, and 127 (3%) stage III. For patients with stage IB disease, SLN micrometastasis was identified by H&E in 173 (84%) and immunohistochemistry (IHC) in 34 (16%); suggesting that 16% would have been staged IA if enhanced evaluation had not been performed. Median follow-up was 6.1 yrs (range 0-17.2). The 5-yr RFS,DSS and OS rates for patients with stage IB disease were 98.0%, 99.5%, and 95.9% respectively, which did not differ significantly from patients with stage IA disease who had 5-year RFS,DSS and OS rates of (97.5%, p=.9), (98.8%, p=.7) and (96.2%, p=.8). When all stage I patients (IA and IB) were evaluated by ER status or grade (grade 1 vs 2 vs 3), these biologic factors were able to significantly discriminate patients with respect to RFS, DSS and OS. Conclusions: Differentiating patients with micrometastases from node negative patients does not stratify patients with respect to survival. Biologic factors (ER status and grade) are better discriminants of survival than the presence of small volume nodal metastases in patients with early stage disease. These data do not support routine use of IHC or alterations in adjuvant therapy decisions based on identification of SLN micrometastases.