Purpose: To evaluate how implementation of the 2003 American Joint Committee on Cancer (AJCC) staging system will affect stage-specific survival of breast cancer patients.
Patients and methods: Records of 1,350 patients treated on sequential institutional protocols with mastectomy and adjuvant doxorubicin-based chemotherapy were reviewed. Pathologic stage was assigned retrospectively according to the 1988 and the 2003 AJCC staging criteria. Overall stage-specific survival (OS) was calculated using the Kaplan-Meier method, and hypothetical differences were compared by the log-rank test.
Results: Six hundred five of 1,087 patients with stage II disease according to the 1988 classification system had stage II disease according to the 2003 system. The 10-year OS for patients with stage II disease was significantly improved using the 2003 system (76% [2003] v 65% [1988]; P <.0001). Two hundred eighty-nine of 633 patients with stage IIb disease using the 1988 system were stage IIb with the 2003 system, and 10-year OS was 58% (1988) versus 70% (2003; P =.003). The number of patients with stage III disease increased from 207 (1988) to 443 (2003), and the 10-year OS changed from 45% (1988) to 50% (2003; P =.077). Most of this difference resulted from changes within stage IIIa: OS, 45% (1988) versus 59% (2003; P <.0001).
Conclusion: Stage reclassification using the new AJCC staging system for breast cancer will result in significant changes in reported outcome by stage. It is imperative that careful attention is devoted to this effect so that accurate conclusions regarding the efficacy of new treatment strategies can be drawn.