Torsten O. Nielsen, MD, PhD, FRCPC, a professor of pathology at the University of British Columbia, discusses the differences between the PAM50 assay and other approved molecular tests for patients with breast cancer.

Most molecular tests, Nielsen says, are very specific for the patient sets from which they were derived and the type of treatment that patients receive. PAM50 is different because it is a biological test that identifies the intrinsic subtypes of breast cancer, Nielsen says. The PAM50 assay is likely to provide relevant information in different types of breast cancer and in different treatment settings.

Nielsen says there are currently clinical trials that are comparing PAM50 with other tests and applying PAM50 to other types of specimens.

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Dr. Nielsen Discusses the PAM50 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.

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

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.

Torsten O. Nielsen, MD, PhD, FRCPC

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Dr. Nielsen Discusses the PAM50 Assay

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

Dr. Nielsen Discusses Using a Ki67 Assay in Breast Cancer