Ki67 Testing on Breast Tumors: Is it Reliable?

Breast cancer. Image made by Itayba
Breast cancer. Image made by Itayba (Photo credit: Wikipedia)

In breast cancer, a measure of a proliferation marker known as Ki-67 has potential for use in clinical management. In fact, if you have breast cancer, you may see a Ki-67 proliferation index result. However, there has been a lack of consistencies among laboratories, limiting its clinical value. In this context, a working group was assembled to devise a strategy to make analysis more consistent.

The Study: Eight laboratories received 100 breast cancer cases, arranged into 1mm core tissue microarrays. One set was stained by the participating lab, and one by the central lab. Sources of variation were analyzed, as was reproducibility.

Results: Within lab reproducibility was high, but reproducibility when comparing labs only moderate (intraclass correlation coefficient 0.71 for central staining; 0.59 for local staining of the specimen). Factors contributing to differences (discordance ) among labs included tumor region selection, counting method, and subjective assessment of how much the cells were staining.

Conclusions: Unfortunately, there is substantial variability in Ki-67 scoring, even among some to the world’s most experienced laboratories [this was an international study]. K67 values and cutoffs for clinical decision-making cannot be transferred between laboratories. We need standardization before we can fully integrate Ki-67 scores into clinical decision-making. I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad:  Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: Journal of the National Cancer Institute 2013, Nov 7 [Epub ahead of print]

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