Ki-67 expression gives additional prognostic information on St. Gallen 2007 and adjuvant! online risk categories in early breast cancer

Background: We sought to determine the significance of Ki-67, one of the tumor cell proliferation markers, as a useful prognostic factor in early breast cancer. Methods: A total of 1080 consecutive patients with stage I or II breast cancer that underwent surgery between 1998 and 2003 were enrolled. Patients were categorized on the basis of the 2007 St. Gallen consensus and Adjuvant! Online. The expression of Ki-67 in the tumor was assayed by immunohistochemistry (cutoff value, 10%). Results: Univariate analysis determined that tumor size, lymph node involvement, histologic grade, estrogen receptor, progesterone receptor, bcl-2, and Ki-67 (≥10%) were statistically significant for both overall survival (OS) and distant metastasis-free survival (DFS). Of these factors, lymph node involvement and high Ki-67 expression were identified as independent prognostic factors for OS and DFS on the basis of multivariate analysis. The survivals of intermediate- and high-risk groups according to 2007 St. Gallen consensus were further separated by Ki-67 expression level (5-year DFS rate = 91.9% vs. 86.3% for Ki-67 < 10% and ≥10%, respectively in intermediate-risk group (P = .01); 5-year DFS rate = 82.5% vs. 61.4% for Ki-67 < 10% and ≥10%, respectively in high-risk group (P = .01)). The survivals of low- and high-risk groups according to Adjuvant! Online were further separated by Ki-67 expression level (5-year DFS rate = 97.8% vs. 89.5% for Ki-67 < 10% and ≥10%, respectively in low-risk group (P = .02); 5-year DFS rate = 9.4% vs. 82.6% for Ki-67 < 10% and ≥10% in high-risk group (P = .005)). Conclusions: Ki-67 is an independent prognostic factor for DFS and OS in early breast cancer and can provide additional prognostic information on the risk stratification with the use of the 2007 St. Gallen consensus and Adjuvant! Online.