The 2003 revised TNM staging system for breast cancer: Results of stage re-classification on survival and future comparisons among stage groups

Background: Changes to TNM staging criteria for breast cancer, introduced in 2003, have resulted in stage re-classification for some tumors. The most frequently implemented change has resulted in tumors associated with more than three positive axillary nodes being upstaged.We hypothesize these TNM staging changes would result in more TNM Stage IIB, IIIA, and IIIB tumors and that disease-specific survival estimates would change under the new staging system. Methods: A review of data was completed for patients diagnosed with breast cancer between 1 January 1995 and 31 December 2000. Tumors that would have been staged differently under the 2003 system were identified and re-classified.Clinical outcomes were determined and disease-specific survival estimates were compared relative to TNM Stage using the old and new staging systems.Data were analyzed using the log-rank test and the method of Kaplan and Meier was used to generate survival curves. Results: Data were available for 2492 tumors, of which 919 were candidates for re-classification, including 829 old Stage II, 59 old Stage III, and 31 old Stage IV. Of these 919, 159 (17%) underwent stage re-classification using the new system. Separate survival estimates for patients who had been under old stage IIA/B, IIIA/B were generated; patients upstaged from IIA or IIB demonstrated a significant difference in survival. Conclusions: Stage specific survival curves indicated decreased survival for patients whose tumors had been upstaged from IIA or IIB under the old system; survival for all other patients remained unchanged.