No Utility of AJCC Stage IA vs Stage IB Designation in Breast Cancer
In a study reported in the Journal of Clinical Oncology, Mittendorf et al found no differences in recurrence-free, disease-specific, or overall survival between patients with American Joint Committee on Cancer (AJCC) stage IA breast cancer and those with stage IB disease. Estrogen receptor status and tumor grade significantly stratified patients with stage I disease with respect to these outcomes.
The seventh edition of the AJCC staging system differentiates patients with T1 tumors and lymph node micrometastases (stage IB) from those with T1 tumors and negative nodes (stage IA).
Study Details
The study involved AJCC staging of 3,474 patients treated at MD Anderson Cancer Center from 1993 to 2007 and 4,590 patients from the American College of Surgeons Oncology Group (ACOSOG) Z0010 trial and analysis of outcomes in those with stage IA vs IB. Median follow-up was 6.1 years and 9.0 years in the two cohorts.
Stage IA vs IB
In the MD Anderson Cancer Center cohort, for stage IA vs IB, recurrence-free survival was 97.5% vs 98.0% at 5 years and 95.4% vs 94.8 at 10 years (hazard ratio [HR] = 1.1, P = .90), disease-specific survival was 98.7% vs 99.5% at 5 years and 95.8% vs 94.0% at 10 years (HR = 1.2, P = .70), and overall survival was 96.2% vs 95.9% at 5 years and 89.1% vs 87.5% at 10 years (HR = 1.1, P = .80).
In the ACOSOG Z0010 cohort, for stage IA vs IB, recurrence-free survival was 95.5% vs 97.0% at 5 years and 92.4% vs 91.6 at 10 years (HR = 1.03, P = .89), disease-specific survival was 99.3% vs 98.9% at 5 years and 98.9% vs 98.3% at 10 years (HR = 1.52, P = .35), and overall survival was 96.6% vs 96.7% at 5 years and 91.7% vs 93.8% at 10 years (HR = 0.69, P = .13).
Estrogen Receptor Status and Tumor Grade
Estrogen receptor status and tumor grade significantly stratified patients with stage I disease. Hazard ratios for estrogen receptor–negative vs estrogen receptor–positive patients were 3.1 (P < .001) for recurrence-free survival, 3.4 (P < .001) for disease-specific survival, and 1.5 (P = .03) for overall survival in the MD Anderson cohort and 2.49 (P < .001), 3.26 (P < .001), and 1.47 (P = .02), respectively, in the ACOSOG cohort. Hazard ratios for grade II and III vs grade I were 2.7 and 5.4 (P < .001) for recurrence-free survival, 2.2 and 6.3 (P < .001) for disease-specific survival, and 1.1 and 1.7 (P = .017) for overall survival in the MD Anderson cohort and 1.59 and 3.13 (P < .001) for recurrence-free survival, 5.29 and 15.42 (P < .001) for disease-specific survival, and 1.10 and 1.77 (P = .0017) in the ACOSOG cohort.
The investigators concluded: “Among patients with T1 breast cancer, individuals with micrometastases and those with negative nodes have similar survival outcomes. [Estrogen receptor] status and grade are better discriminants of survival than the presence of small-volume nodal metastases. In preparing the next edition of the AJCC staging system, consideration should be given to eliminating the stage IB designation and incorporating biologic factors.”
Elizabeth A. Mittendorf, MD, PhD, of The University of Texas MD Anderson Cancer Center, is the corresponding author for the Journal of Clinical Oncology article.
The study was supported in part by grants from the National Cancer Institute. For full disclosures of the study authors, visit jco.ascopubs.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
