Implications for Breast Cancer Restaging Based on the 8th Edition AJCC Staging Manual

Abstract

Objective: We assessed the changes that have resulted from the latest breast cancer staging guidelines and the potential impact on prognosis.

Background: Contemporary data suggest that combining anatomic staging and tumor biology yields a predictive synergy for determining breast cancer prognosis. This forms the basis for the American Joint Committee on Cancer's (AJCC) Staging Manual, 8th edition. We assessed the changes that have resulted from the new staging guidelines and the potential impact on prognosis.

Methods: Women with stages I to III breast cancer from 2010 to 2014 in the National Cancer Data Base were pathologically staged according to the 7th and 8th editions of the AJCC Staging Manual. Patient characteristics and restaging outcomes were summarized. Unadjusted overall survival (OS) was estimated, and differences were assessed. Cox proportional-hazards models were utilized to estimate the adjusted association of stage with OS.

Results: After restaging the 493,854 women identified, 6.8% were upstaged and 29.7% were downstaged. The stage changes varied by tumor histology, receptor status, tumor grade, and Oncotype DX scores (all P < 0.0001). Applying the 8th edition criteria yielded an incremental reduction in survival for each increase in stage, which was not consistently seen in the 7th edition. In a subgroup analysis based on hormone receptor (HR) status, those with stages II and III, and HR- disease had a worse OS than those with HR+ disease.

Conclusions: Applying the 8th edition staging criteria resulted in a stage change for >35% of patients diagnosed with invasive breast cancer and refined OS estimates. Overall, the transition to the 8th edition is expected to better drive clinical care, treatment recommendations, and future research.

FIGURE 1.

Patient selection diagram from the National Cancer Database (NCDB) from 2010 to 2015, applying the defined inclusion and exclusion criteria.

FIGURE 2.

Unadjusted overall survival analysis for breast cancer using the AJCC Cancer Staging Manual 7th and 8th editions for stages IA to IB (A: 7th edition; B: 8th edition) and stages IIA to IIIC (C: 7th edition; D: 8th edition).

FIGURE 3.

Unadjusted overall survival analysis for breast cancer stages I to III using the AJCC Cancer Staging Manual 7th (A, C, E) and 8th (B, D, F) editions for all patients, subdivided to stage (A and B: stage I; C and D: stage II; E and F: stage III). Hormone receptor (HR) status defined as HR+ if estrogen receptor (ER) + and/or progesterone receptor (PR) +; defined as HR− if ER− and PR−.

FIGURE 4.

Unadjusted overall survival analysis for breast cancer stage I using the AJCC Cancer Staging Manual 7th (A, C, E)and 8th (B, D, F) editions for all patients (A and B) with subgroup analysis by age <50 (C and D) or ≥50 years old (E and F).