Dr. Nielsen on the Pros and Cons of the Ki67 Assay

Torsten O. Nielsen, MD, PhD, FRCPC, a professor of pathology at the University of British Columbia, discusses the pros and cons of using the Ki67 as a prognostic marker in breast cancer.

Nielsen says there is extensive literature on the clinical validity of Ki67. It is a marker of proliferation that assists in the prognosis of breast cancer and many believe an assay could have a role in the prediction of the disease. Nielsen also notes that testing for Ki67 could be a substitute for a more complex, expensive test.

However, the Ki-67 tumor marker test is not without problems, Nielsen says. There is poor analytical reproducibility with Ki67 scores, especially within the critical 10-20% range.

Although the fundamentals of the assay work well, Nielsen says, the scoring and interpretation of the test are difficult to reproduce.