Evaluation of comparative survival based on the AJCC 5th and 6th editions for breast cancer staging: 25 year experience in two southwest Washington state community cancer programs

Abstract

6118 Background: The revised American Joint Committee on Cancer (AJCC) sixth edition (6th ed.) cancer staging system increased stratification within breast cancer (BC) stages II and III defined by the AJCC 5th ed. system. The specific aim of this study was to determine and compare disease-free survival (DFS) for stage 0-III breast carcinoma between the 5th and 6th editions using retrospective data gathered from 1980–2004 in southwest Washington state (WA). Methods: 4,810 patients (pts) were identified using cancer registries at Saint John Medical Center in Longview, WA and Southwest Washington Medical Center in Vancouver, WA. Patients were restaged retrospectively using the 5th and 6th ed. systems. DFS was determined using the Kaplan-Meier method and compared using the log-rank test. Results: The age at diagnosis ranged 20–99 yrs, with a mean age = 60. The mean length for disease-free follow-up was 224 mos. Stage 0 and stage 1 criteria were unchanged between editions, and 10-yr DFS was 94% and 87% for stage 0 and stage 1, respectively. In stage II pts, 13% (199/1,519) were upstaged to stage III by the 6th ed. criteria, significantly improving the 10-yr DFS for stage II from 66% (5th ed.) to 72% (6th ed; p = 0.003). The majority, 85% (167/199), of pts upstaged were from the 539 classified as stage IIb disease by the 5th ed. This accompanied an increase in the 10-year DFS for stage IIb from 54% (fifth) to 62% (sixth; p = 0.046). The number of pts with stage III disease increased from 313 to 588 in the 6th ed. 10-year DFS increased from 30% to 36% (p = 0.025), respectively. Most of this increase resulted from changes within stage IIIa, as DFS increased from 32% to 41% (p = 0.046). When compared, DFS outcomes between stage IIIb and IIIc were not found to be statistically significant (p = 0.501). Conclusions: The AJCC 6th ed. system for BC provides greater distinctions between stages compared to the 5th ed., and reclassification results in significant changes in projected outcomes. However, the addition of the IIIc substage does not seem to show the same significant distinction when compared to the existing stage IIIb substage in outcomes. No significant financial relationships to disclose.