Skin

Because PDT has only had approved sensitizers that are activated with somewhat shallowly penetrating wavelengths (600+nm ranges) the typical indications that are in use are heavily weighted toward skin conditions and therapies. Even then the few that are approved are 'crippled' ones that are not ideal such as 'ALA', aminolevulinic acid, which is not even a photosensitizer. It is a precurser to a naturally occuring photosensitizer the body makes called PPIX or PP9. So the approved medicine is a pale shadow of what is possible with modern photosensitizers. The approval process seems to be affected by those who do not want the see the full potential of skin PDT realized. Even the poor sensitizer Photofrin which was approved nearly 3 decades ago after 17 years in the regulatory 'quicksand' process and for which the single dosage is priced at 20,000$+ (a pig blood derivative) took nearly another half dozen additional years to be approved for skin usage because of what some feel were objections by Dermatologists who felt it would threaten their legacy-based practices.

Skin Cance

Skin cancer and the role of PDT

A number of different types of skin cancer have been treated using a variety of PDT methods. These include primary skin cancers, where the tumour originates within the skin itself, and secondary (or metastatic) tumours where the disease has its origins in another site. Primary skin cancer is the second most common type of cancer in the UK (after the lung) with the three predominant forms originating from different types of cells found within the outer (epidermal) skin layer - resulting in basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma (MM). Whilst being irritating and visually unpleasant the first two conditions are not fundamentally life threatening, but may eventually spread unless treated.

The malignant melanoma is a much more serious disorder, as the potential for its development to greater depth facilitates rapid metastasis. It should be noted that a case of malignant melanoma is curable only if identified at an early stage, with surgical excision being the standard form of treatment. PDT is not considered to be a treatment option for this condition, principally because these lesions are highly pigmented and therefore do not allow effective light penetration.

Psoriasis

Psoriasis is a non-contagious, lifelong skin disease affecting 4.5 million adults in the United States. Because there is no cure for psoriasis, multiple treatment options currently available only attempt to reduce the severity of symptoms. PDT and SPDT show promise to be effective treatments for this unfortunate condition.

Actinic (Sun) Damage

There is substantial evidence linking the role of ultra-violet radiation from the sun in the development of superficial cancers. Early sun-induced changes in the skin may be classified as actinic keratoses (AK) that generally consist of scaly discoloured patches, most often found on the face and scalp of fair skinned adults. If not treated they can develop into cancers - approximately 40% of BCCs develop from AKs.

Acne

Acne is the most common skin disease in the world, affecting more than 90 percent of adolescents. In the US alone, over 45 million have acne and 13 million have rosacea. 85% of people worldwide suffer from acne at some point in their lives, leading to more than 103 million affected by acne and another 45 million by rosacea. Teenagers develop acne at a higher rate than other age groups because hormone production during puberty increases the output of the sebaceous glands and the rate of skin-cell turnover within the follicles. PDT acne therapy can even work in patients who have failed accutane, the currently accepted treatment for severe acne. Accutane also targets the sebaceous gland but accutane has fairly toxic side effects. PDT is a very safe alternative to accutane treatment.