Potential applications of photodynamic therapy

At the present time, photodynamic therapy (PDT) is under active investigation for a range of therapeutic applications, in both oncology and nononcology areas of medicine. In oncology, a number of studies have indicated that PDT has potential in the laser treatment of malignant tumours. In addition, PDT may be used preoperatively to increase operability, and reduce the extent of required resection, in the surgical treatment of lung cancer. The results of preclinical investigations have suggested that PDT may be useful in bone marrow purging to eliminate malignant cells prior to marrow transplantation, and clinical trials are now underway to examine this further. A particularly successful use of PDT is likely to be for the treatment of Barrett's oesophagus where malignancy may involve long sections of oesophagus, with multifocal and unpredictable distribution. A number of nononcological applications for PDT have been proposed. For example, initial studies suggest that it may reduce nonchoroidal neovascularization in ocular vascular disease. PDT has also been investigated for use in treating atherosclerotic cardiovascular lesions or to prevent restenosis following balloon angioplasty, again with encouraging results. Under certain conditions, PDT may modulate immunological processes, as a result of the destruction of immunologically active cells; it has been proposed that this property could be utilized to relieve rheumatic symptoms by down-regulating the cellular immune response in rheumatoid arthritis. Selective destruction of pathological synovium, whilst leaving articular surfaces undamaged, may also be achieved by appropriate use of PDT. PDT may have some applications in virology; its uses against papilloma virus and against HIV and bloodborne viruses are still under investigation. The accessibility of skin to light offers an opportunity for the use of PDT in the treatment of dermatological conditions; early studies suggest that it can be helpful in psoriasis, whilst its uses in acne, alopecia areata, portwine stains and hair removal are also being investigated. The next few years will certainly see an expansion of the indications for PDT.