Background: Several studies have emphasized Ki67LI biologic and prognostic value and its potential application of its assessment in routine practice, particularly to define prognostic subgroups of luminal/hormone receptor-positive (HR+) tumors.

Methods: Ki67LI was identified by immunohistochemical staining in 3760 EBC pts treated from 1995 to 2008. Median age was 61 y. The relationship with clinic-pathological parameters and the prognostic significance of KI67LI were investigated in all EBCs and in HER2 negative luminal (2380 HNL) cases stratified on homogeneous grading (594 G1, 1282 G2, 504 G3).

Results: Median Ki67LI values were 22% in all cases, 20% in HNL and 10, 20 and 35% in different HNL grading group (HNL-GG).

Ki67LI > 22% (1873 pts) was significantly (p<0.001) associated with younger age, ductal type, greater size, positive N, poor G, absent or low ER /PR expression, positive HER-2, triple negative subtypes.

Local and Distant Relapses were 138 (7.3%) and 355 (18.9%) in < or > 22% Ki67LI respectively. Median time to first event was 31.7 ms in > 22% vs 50.1 ms in < 22% Ki67. At median f-up of 77 months EFS and OS were 91.9 and 92.1% in < 22% vs 78.9% and 81% in > 22% Ki67 respectively (p <0.001).

Prognosis in term of DFS and OS was consistently worse for > 22% compared to < 22% Ki 67 in all clinical-pathological subsets, except in negative ER group. In multivariate analysis, KI 67mantained an independent prognostic significance for DFS and OS.

In HNL, EFS and OS were 93.7 and 92% in < 20% vs 81.7 and 83.3% in >20% Ki67(p <0.001). Using median ki67LI value for different homogenous HNL-GG as cutoffs, we stratified these populations in low and high risk. The results are shown in the following table.

Stratification in high and low risk subgroups of homogeneous HNL-GG

Subgroups EFS OS 
G1 high 91.7% 0.043 92.7% 0.114 
G1 low 96.0%   96.0%   
G2 high 84.2% <0.001 87.5% 0.012 
G2 low 93.7%   90.6%   
G3 high 70.9% 0.053 76.4% 0.036 
G3 low 83.2%   80.7%   
Subgroups EFS OS 
G1 high 91.7% 0.043 92.7% 0.114 
G1 low 96.0%   96.0%   
G2 high 84.2% <0.001 87.5% 0.012 
G2 low 93.7%   90.6%   
G3 high 70.9% 0.053 76.4% 0.036 
G3 low 83.2%   80.7%   

Conclusions: Our study confirms prognostic value of Ki67LI in EBC, associated with other clinical-pathological characteristics. Cutoffs are different into HNL-GG. They can cathegorize at least two biological entities in every grading group providing additional prognostic information in planning therapies and outcome prediction.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-53.