Photodynamic Therapy (PDT)

What is photodynamic therapy (PDT) ?

• It is a technique which consists of producing activated oxygen by using a photsensitizing substance combined with a source of light.

How does it work ?

• Applying a cream (containing aminolevulinic acid) enables it to combine with porphyrins. The latter then become activated thus susceptible to light.
• Their reaction wih light produces “oxygen singulets”, which have the possibility (among others) to induce cell death (through necrosis and apoptosis) and to kill germs.

When is PDT used ?

• It is classically used in the treatment of precancerous skin conditions (actinic keratosis) and of certain skin cancers.

How much time does it take ?

• Before the cream is applied, the doctor will take away the superficial layer of the skin to enable the cream to penetrate.
• Then, one needs to wait for the cream to penetrate and react with porphyrins (around 3 hours, but some recommend a longer wait, sometimes overnight).
• A source of light is then shone for a duration of 10 to 15 minutes. (There is also PDT with natural sunlight, in which case up to 2 hours may be needed).
• For the whole process, half a day is usually needed (however it may vary).

Does it hurt ?

• One needs to know that PDT causes pain when the source of light is shone.
• The pain can be more or less severe.