Abstract P1-01-06: Evaluation of the stage IB designation of the 7th edition of the AJCC staging system: Biologic factors are more important

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Abstract Purpose: The stage IB designation was added to the AJCC 7th edition staging system to denote micrometastasis in patients with T1 tumors. We have previously examined this group and found that receptor status and nuclear grade were better survival discriminates than the presence of micrometastases. The current study was undertaken to validate this finding in a larger cohort from the American College of Surgeons Oncology Group (ACOSOG) Z0010 study. Methods: Clinicopathologic and outcomes data from patients enrolled on ACOSOG Z0010 were recorded. All patients underwent breast conserving surgery, sentinel lymph node biopsy and whole breast radiation for clinical T1-2, N0 breast cancer. Sentinel lymph nodes were evaluated by H&E locally and if negative, by immunohistochemistry (IHC) at a central laboratory. Patients were staged according to the 7th edition AJCC system and 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: There were 5210 eligible and evaluable patients enrolled on ACOSOG Z0010. AJCC stage distribution was known in 4590 and included: 2849 (62.0%) stage IA, 376 (8.2%) stage IB, 878 (19.1%) stage IIA, 322 (7.0%) stage IIB, and 170 (3.7%) stage III. Median follow-up for the cohort was 9.0 years (range 0–12.6). Five and 10-year RFS, DSS and OS rates for patients with stage IA versus IB disease are shown in table 1. There were no significant differences between groups. When all stage I patients (stage IA and IB) were evaluated by ER status (positive vs negative) or grade (grade 1 vs 2 vs 3), these biologic factors were able to significantly discriminate patients with respect to RFS, DSS and OS (table 2). Conclusion: Differentiating patients with micrometastases (stage IB) from node negative patients (stage IA) does not stratify patients well with respect to survival. Biologic factors including ER status and grade are better discriminants of survival than the presence of small volume nodal metastases in patients with early stage breast cancer. Breast cancer staging should include biologic factors from the primary tumor. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-01-06.