Molecular imaging probes for cancer research. PET and SPECT in Cancer Theragnostics

The optimal drug regimen in cancer therapeutics is one with the best chance to cure an individual patient while reducing risks and toxicity. Major determinants of individual tumor response to a given therapeutic regimen are the specific gene expression profile of the tumor, the characteristics of tumor microenvironment and some host-related factors. Therefore any diagnostic test capable of identifying components of these major determinants that are known to be associated to a good or poor response to therapy as well as to the occurrence of side effects may contribute to the tailoring of an optimal drug regimen for a single patient. The term theragnostics is defined as the integration of a diagnostic test with a specific therapeutic intervention. The diagnostic test should identify patients who will likely respond to a particular therapy, fail to respond to a given drug or eventually exhibit adverse events. The test may also be valuable for monitoring the individual response to a specific treatment. The diagnostic test may be either based on high-throughput technologies such as genomics, transcriptomics, proteomics, pharmacogenomics or on conventional diagnostic techniques. In the “omics” approach the test identifies an array of genes or their products that predict tumor response or adverse side effects. In the conventional approach the test identifies well-known prognostic markers of good or poor response to therapy or molecules involved in the mechanisms of drug sensitivity and resistance.