Prognostic Stage Groups Established by AJCC Staging System 8th Edition Does Not Significantly Improve Discrimination Over Classic TNM Staging in Early Stage Breast Cancer Treated With Breast Conservative Therapy

Abstract

The new AJCC staging system 8th edition established the prognostic stage groups for breast cancer, which incorporates biomarkers into classic TNM system to improve discrimination over anatomic stage group. This study is to verify whether AJCC Stage staging system 8th edition is superior to 7thin early stage breast treated with breast conservative therapy, and help to individualize their treatment. 1602 patients with T1-2N0-1M0 breast cancer treated from 1999 to 2013 were retrospectively reviewed. All underwent breast conserving surgery plus axillary lymph node dissection or sentinel node biopsy without neoadjuvant chemotherapy. 1220 patients who had complete information on histological grade, ER, PR and Her2 status were included in this analysis. The median age was 46 years (range, 20-84). 1054 (86.4%) received radiotherapy, 900 (73.8%) received hormone therapy, and 91 (7.5%) received trastuzumab targeted therapy. All patients were restaged according to the new AJCC staging system 8thedition. Locoregional recurrence (LRR), disease free survival (DFS) and overall survival (OS) were calculated by using the Kaplan-Meier method and compared by log-rank test. With a median follow-up of 47 months (IQR, 34-74months), the overall 5-year LRR was 3.6%, 5-year DFS was 93.4%,and 5-year OS was 99.2%. By AJCC 7th staging system, 803 (65.8%) patients had stage IA and 417 (34.2%) had stage IIA diseases. Patients with stage IIA had significant lower DFS than stage IA, but there were no significant difference in OS and LRR between the two groups (Table 1). By AJCC 8th staging system, 608 (49.8%) patients were assigned to a different group, with 250 (41.1%) to a lower stage and 358 (58.9%) to a higher stage. AJCC 8th staging system can help identify a group of patients such as IIIA with significant worse LRR and DFS, but didn’t improve discrimination on OS as compared with AJCC 7th staging system ( Table 1 ). For early stage breast cancer treated with breast conservative therapy, AJCC 8th staging system doesn’t significantly improve discrimination over classic TNM staging. It might need further investigation on prognostic biomarkers.Abstract 2016; Table 1Five-Year Outcomes According to Different Stage GroupsNo. (%)5year-LRR (%)5year-DFS (%)5year-OS (%)Stage7th8th7th8th7th8th7th8thIA803 (65.8)554 (45.4)2.62.194.796.099.199.6IB395 (32.4)4.191.298.8IIA417 (34.2)162 (13.3)5.33.190.894.099.498.8IIB54 (4.4)4.093.097.4IIIA55 (3.4)15.681.593.8P value0.118<0.0010.016<0.0010.5730.291 Open table in a new tab