The points of action (targets) of the tumour or the metastases – some of which have been shown above – can be identified by a so-called chemosensitivity testing. For this purpose the activity (or expression) of a great number of genes is quantified that are responsible for the heightened metabolism, increased energy supply and cell-to-cell communication of the tumour. The data are then rechecked by gene mutation analysis and in the proteome measuring the amount of newly produced proteins (e.g. responsible for cell to cell communication), which corresponds to the gene expression and gene mutation.

In chemosensitivity testing the optimal medication or combination of drugs for the respective patient is thus determined taking the complete bunch of all approved drugs in consideration according to the respective tumour type.

The data assist the attending doctor both in his diagnosis and in his choice of an optimal, highly individualised therapy.

The basis of increased gene expression is sometimes a mutation of the parent gene. For instance the EGF receptor can have a mutation in G719L Exon 18. This mutation produces an increased gene expression of EGFR which can be measured by RT-PCR. RT-PCR gives not only the information about increased expression but allows also a relative quantification of the data. By means of that information one can estimate whether the used communication pathway is main street or by-road.

Some mutations show no increased gene expression (e.g. silent mutations).Therefore it is indispensable to determine the gene expression besides mutation analysis.