Interpretation of treatment results with biological agents: is there a need for a new methodology?

The biological basis of cancer is progressively being demonstrated at a molecular level and it is possible to model the process of cancer and identify the points at which therapeutics can operate. With this knowledge of function, it is no longer satisfactory to assess response to therapy simply by change in dimensions of cancer. Genomic and proteomic analysis adds to conventional pharmacokinetics and pharmacodynamics in preclinical models and at selected points in clinical development but advances in functional imaging make this a key tool for assessing response to therapy. Functional analyses of computed tomography (CT) and magnetic resonance imaging (MRI) images can add important information about tumour patho-physiology and positron emission tomography (PET) and single photon emission tomography (SPECT) imaging make it possible to study the distribution and therapeutic function of drugs. Together these advances will improve clinical practice and facilitate effective and safe drug development.