Photodynamic Therapy (or PDT) has been utilised for quite a few years. There have been applications in treating psoriasis to induce remissions, some types of lung and other cancers, and now more recently in treating sun damage problems of both non-cancerous and cancerous types.
The idea behind all these modalities is the introduction of a molecule into a particular issue that needs treatment. Once introduced it is converted into its active form by irradiating with light at the most appropriate wavelength for the molecule.
PDT With Metvix
At Springdale Clinic the molecule introduced is methyl aminolevulinic acid (Metvix). Straight aminolevulinic acid (ALA) has been used for a few years. ALA is water soluble and not very lipid (or fat) soluble, which poses a problem in absorption through the skin. It takes longer for effective concentrations to get through and seems more diffuse in its spread. And careful cleansing of the skin is required to improve the absorption. Natural skin oils are cleaned away before application.
As methyl ALA is lipid soluble it does not require the same careful cleansing before application and absorbs very rapidly and locally. This allows less time for ambient light to prematurely activate the molecule.
On absorption into the tissues ALA and methyl ALA cause the accumulation of protoporphyrin IX which has a number of light absorption peaks that will convert it to its next molecule releasing singlet oxygen radicals which oxidise the cells they are in, selectively destroying them.
The various light peaks that are available to activate the molecule are in the blue, green, yellow and red areas of the spectrum.
Blue light has been used as an acne treatment utilising the naturally occurring protoporphyrin IX in the bacteria that lives in acne pustules. This will cause destruction of those bacteria.
But a lot of acne lesions do not have the bacteria present and the action is more at this level than the sebaceous gland activity itself. This explains why blue light therapy has had such a limited effectiveness in acne therapy.
Blue Vs Red Light
ALA is recommended activated by blue light – this is the strongest absorption peak. But the shorter the wavelength of light the less distance it penetrates into the skin. Metvix is recommended activated by red light, which allows deeper penetration. As sebaceous glands are not very superficial in the skin this seems more logical for this treatment. Also where Metvix is used to treat basal cell carcinomas, the longer wavelength will penetrate deeper into the carcinoma ensuring a better activation through its depth.
Helium Neon Laser Activation
By using the Helium Neon laser at Springdale we benefit from the special properties of laser that make it in all therapeutic situations more effective than broad spectrum light or even narrower spectrum LED light. Laser has particular peaks of power within it as it interacts with the environment. This gives the laser light its peculiar speckles. With these intense peaks that shift with time greater local power is achieved throughout the tissue than will occur with regular light production.
There have been comments from people employing regular or LED red light that the treatment can be quite uncomfortable. We have never experienced this with our treatments. And yet they are very effective. Full activation of the protoporphyrin X can be checked by its fluorescence with ultraviolet light. After laser irradiation there should be no obvious fluorescence. Therefore there is no need to avoid further exposure to sun or other strong lights which is sometimes recommended by some clinics.
Solar Keratosis & Basal Cell Carcinoma Treatment
The actual problem needs to be identified first. If there is doubt about an area being a simple solar keratosis as opposed to something more sinister, a punch biopsy will be performed and the result checked before treatment. All basal cell carcinomas will have a punch biopsy performed to ensure they are the type that will respond to Metvix PDT.
Three hours before the session, the Metvix cream is applied. If the aim is to clear a wide area of solar keratoses including future as yet unseen ones, then the whole area will be covered. Otherwise the lesions themselves only will be treated. Areas under clothing will often have some plastic dressing applied to ensure the cream absorbs into the skin rather than the clothing. Instructions are given to avoid getting the area exposed to strong light, direct and reflected sunlight.
After the three hour absorption, the area is scanned by the Helium Neon beam of the laser for a number of minutes to activate it. The larger the area, the longer will be the time required. After this any excess cream can be removed and the patient can go home. By allowing the lesions to shed naturally, any long term marks or scars should be avoided.
A second treatment is recommended within two to three weeks depending on the area. With basal cell carcinomas the area should then be monitored to ensure clearance. If there is any question then a further biopsy should be preformed.
The treated area can appear red to pink for some weeks afterwards. If a basal cell carcinoma does not clear in two treatments it is usual practice to excise it to clear it definitively.
With acne, as noted above, usually only 20 minutes is required for adequate absorption into the sebaceous glands (we are currently checking the best application time for the best response, but have followed recommendations from other clinics so far).
The area is effectively covered with the cream after any makeup or other skin preparations are removed. After twenty minutes the cream is activated by the Helium Neon beam. Any residual cream is washed away. Another treatment can take place in usually around three weeks.
Normally three or four treatments will be effective in producing a quite long term remission. As mentioned before we can also utilise the 904nm Gallium Arsenide beam at the same time to create some changes in the previously produced acne scars.