Analytical validation of a standardized scoring protocol for Ki67: phase 3 of an international multicenter collaboration.

A simple, low-cost test for breast cancer holds promise for determining prognosis in both well developed and less developed regions of the world where most new cases of the disease now occur. The test measures Ki67, a biomarker that indicates how fast cells are dividing. There have been concerns about the variable results from non-standardized methods but new work showed the potential of a standardized visual method. Mitch Dowsett at the Institute of Cancer Research in London, UK, and his co-workers asked researchers at 22 laboratories in 11 countries to score 30 pre-stained tumor samples for Ki67, using 3 methods that required only a light microscope and a desktop computer. One of the methods showed sufficient between-lab reproducibility but the other two narrowly missed the reproducibility requirements. The findings hint that a simple, globally applicable test for breast cancer is one step closer.