Markers, oncotype and other MOquestions

Hi scaredashell:

I posted some information about ki-67 in another thread yesterday:

. . . Ki-67 is a protein that is a marker of cell proliferation or cell growth (a higher percentage suggests more dividing tumor cells).

In general, rapidly dividing cells may be more responsive to chemotherapy. The 2015 St. Gallen panel commented:

"There can be little doubt that Ki-67 scores carry robust prognostic information [24], and that high values predict the benefit of addition of cytotoxic chemotherapy [25], but definition of a single useful cut point has proved elusive both because Ki-67 displays a continuous distribution [26], and as a result of analytic and preanalytic barriers to standardized assessment [27]."

In other words, despite the results of studies which report some prognostic and predictive value, there are technical issues with determination of ki-67 percentages by standard IHC methods, including interobserver variability (different results when different people perform the test on the same sample) and lack of reproducibility across laboratories, as explained in detail here:

Polley (2013): "An International Ki67 Reproducibility Study"

http://jnci.oxfordjournals.org/content/105/24/1897.full

(Free PDF available via link)

Also, different studies use different values as cut points or cut-offs between what is considered "low" or "high" ki-67.

All of this makes it difficult to rely on the results of clinical studies in which ki-67 was determined in other labs and to interpret the clinical significance of a ki-67 test result based on such studies. Accordingly, some institutions no longer perform ki-67 testing (at this time), and clinical consensus guidelines (e.g., from ASCO) do not generally support the broad use of ki-67 protein (determined by standard IHC) to guide adjuvant chemotherapy decisions.

BarredOwl