Ki67 Index in Breast Cancer: Correlation with Other Prognostic Markers and Potential in Pakistani Patients

Introduction: Breast cancer aggressiveness can be correlated with proliferation status of tumor cells, whichcan be ascertained with tumor grade and Ki67 indexing. However due to lack of reproducibility, the ASCO donot recommend routine use of Ki67 in determining prognosis in newly diagnosed breast cancers. We thereforeaimed to determine associations of the Ki67 index with other prognostic markers like tumor size, grade, lymphnode metastasis, ER, PR and HER2neu status.
Methods: A total of 194 cases of newly diagnosed breast cancerwere included in the study. Immunohistochemical staining for ER, PR, HER2neu and Ki67 was performed bythe DAKO envision method. Associations of the Ki67 index with other prognostic factors were evaluated bothas continuous and categorical variables.
Results: Mean age of the patients was 51.7 years (24-90). Mean Ki67index was 26.9% (1-90). ER, PR, HER2neu positivity was noted in 90/194 cases (46.4%), 74/194 cases (38.1%)and 110/194 cases (56.70%) respectively. Significant association was found between Ki67 and tumor grade,PR, HER2neu positivity and lymph node status, but no link was apparent with ER positivity and tumor size.There wasan inverse relation between Ki67 index and PR positivity, whereas a direct correlation was seen withHER2neu positivity. However, high Ki67 (>30%) was associated with decreased HER2neu positivity as comparedto intermediate Ki67 (16-30%). The same trend was established with lymph node metastasis.
Conclusion: Ourstudy indicates that with high grade tumors, clinical utility of ki67 is greater in combination with other prognosticmarkers because we found that tumors with Ki67 higher than 30% have better prognostic profile comparedto tumors with intermediate Ki67 level, as reflected by slightly lower frequency of lymph node metastasis andHER2neu expression. Therefore we suggest that Ki67 index should be categorized into high, intermediate andlow groups when considering adjuvant chemotherapy and prognostic stratification.