Dr. William Pao explains the caveats of molecular testing in terms of differences in testing methods through different laboratories and the heterogeneity of molecular findings in different biopsies even within the same individual with lung cancer.

[powerpress]

We know that cancer cells mutate over time -- in fact, that's how they became cancer cells. In fact, oncologists see the heterogeneity of cancer cells in our daily practice every day. Although there are certainly many reasons why patients have some of their cancer cells respond and others not (blood supply, local microenvironmental factors, etc.), one of the important factors is genetic heterogeneity within the cancer cell population -- some cells die and others don't.