MKI67 and breast carcinoma: In conducting this study, we followed the recommendations of the Breast International Group and North American Breast Cancer Group Biomarker Working Party for the immunohistochemical assessment of Ki67 labeling index levels and the interpretation of Ki67 labeling index values.26 For example, in the absence of consensus regarding a recommended cutpoint, we considered a conservative cutpoint of 5%, combined with clinical response to the initial treatment with exemestane alone, appropriate for the study population.