The main advantages of this approach include (i) the high likelihood of tumor specimens being molecularly and therapeutically relevant (as opposed to normal “surrogate” tissues); for example, mutations of epidermal growth factor receptor (EGFR) are present in the DNA of tumor tissue of non small cell lung cancer (NSCLC) but not in DNA from normal lung tissue in the same individuals [11], and (ii) the fact that most of the experience in the use of current standard pharmacodynamic assays and methodologies was gained from the use of tumor tissues. Here, EGFR is linked to non-small cell lung carcinoma.