Dr. Nielsen Discusses Using a Ki67 Assay in Breast Cancer

Torsten O. Nielsen, MD, PhD, FRCPC, professor, pathology, University of British Columbia, on using a Ki67 assay for patients with breast cancer.

A Ki67 assay is cheap, easy, convenient, and gives a physician important information about a patient. Ki67 is a convenient immunohistochemical tool for measuring proliferation, which is a critical factor in breast cancer, though there are some issues with analytical validity. If a physician wants to administer a Ki67 test, he/she must internally validate the test and interpretation, demonstrating analytical validity for the clinical indication in question.

In order to adopt a cut point, one must carefully benchmark an interpretation of Ki67 against existing papers and methods in order to make safe clinical decisions, Nielsen says. Otherwise, there remains a chance of significant bias in an assessment of Ki67, resulting in potentially wrong clinical decisions.