Addendum re the direction of personalized medicine:
The discussion in the last few posts illustrates the sharp contrast between older implementations of personalized medicine, such as EGFr-expression screening, and newer implementations, such as testing for the K-ras mutation. The contrast is especially notable in that both implementations are germane to the class of anti-EGFr drugs (Erbitux, Vectibix, and Nimo).
In general, the former kinds of implementations are poorly defined (e.g. EGFr expression is not a true biomarker, but rather an arbitrary cut-off value of an assay) and have weak predictive value, while the latter kinds of implementations are biomarkers in the literal sense of the word and have strong predictive value.
Over time, we should see more and more implementations of personalized medicine that are similar to the K-ras test, and fewer and fewer that are similar to the EGFr screening specified in the FDA labels for Erbitux and Vectibix. This trend pertains not just to the treatment of metastatic colorectal cancer, but also to medicine in general.
“The efficient-market hypothesis may be
the foremost piece of B.S. ever promulgated
in any area of human knowledge!”
