Both Ki-67 and histological grade are established prognostic factors in patients with early breast cancer. Recent international expert consensus employs Ki-67 to classify luminal breast cancer, and histological grade is described as an alternative. We investigated the prognostic value of Ki-67, histological grade, and their combination.Methods
Patients with early breast cancer treated with surgery between January 2000 and December 2008 were retrospectively reviewed. Inclusion criteria were as follows: estrogen receptor positive, HER2 negative, available for Ki-67 and histological grade. Clinicopathological data were retrieved from medical records. Ki-67 labeling index was investigated using MIB-1 antibody and subdivided into three categories: low 0-9%; intermediate 10–19%; high >20%. Histological grade was scored between 1 and 3. Disease-free survival (DFS) was defined as time from surgery to the first documented disease recurrence or death. Ki-67 categories and histological grade were analyzed respectively and then concomitantly for prognostic impact on DFS.Results
A total of 606 patients were included. Median age was 58 and 28.1% were over 65 years. 65.4% were postmenopausal women. Progesterone receptor was positive in 84.0% of patients. 29.6% received neoadjuvant or adjuvant chemotherapy. Number of lymph node metastasis was 0 in 70.0%, 1–3 in 21.3%, and >4 in 8.7% of patients. Ki-67 categories and histological grade showed weak but significantly correlation (Spearman's rho = 0.385, P < 0.001). High Ki-67 and histological grade 3 were correlated with worse prognosis to the same extent (HR 2.518, P = 0.002 and HR 2.541, P = 0.048, respectively). For combined analysis, patients represented concomitant with high Ki-67 and histological grade 3 showed worse prognosis compared with those with Ki-67 low and histological grade 1 (HR 3.137, P = 0.021). Conclusions: Ki-67 and histological grade were significantly but weakly correlated. The combined use of these two factors could better predict recurrence of early luminal breast cancer.