Orthotopic animal models for oncologic photodynamic therapy and photodiagnosis.

Photodynamic therapy is a complex treatment modality where a large array of factors can influence therapeutic outcome. Vascularization, vessel permeability, oxygenation and light distribution in the tissue as well as immune response play a key role in the photodynamic process. Each of these factors can be influenced by the choice of the animal model. It is therefore of the utmost importance to choose an appropriate model for pre-clinical oncologic PDT studies. Orthotopic tumor models present the closest resemblance to the clinical situation with regard to the elements involved in PDT. We present here a brief organ specific overview of the different orthotopic animal models that can be used for in vivo photodynamic therapy studies.