A thousand words about the challenges of photodynamic therapy

The outbreak of interest in photodynamic therapy (PDT) at the end of last century to treat cancer and other diseases was based on the promise of localised treatment, cheaper therapy and fast ablation of the treated organ. One of the most attractive features of PDT is that it can evade cancer’s resistance to photosensitisers. PDT for cancer therapy depends on the absorption of a photosensitiser within the malignant tissue. The photosensitising drug is then activated by light (usually from a laser) and the active drug destroys the targeted tissue. However, one must consider that this is a complex mechanism involving many factors such as the diverse light and oxygen distribution in the treated organs, which has mitigated application of this technique in clinical practice. PDT is not a simple treatment that can be done by eyeballing; it requires precise planning that can be done with the help of complex computer programs. Computer simulation of PDT to optimise treatment depends heavily on intense calculations in all steps of the procedure, and desktop computers are only now sufficiently powerful to assist physicians during therapy in real-time. In this mini-review, the challenges of photodynamic therapy are described, and possible to solutions to overcome these are presented.