PHOTODYNAMIC THERAPY (PDT) INFORMATION
Compiled by Dr. D.K. Whitaker, Dermatologist
You have been prescribed PDT or Photo Dynamic Therapy - so how exactly will you be treated?
POT is a non-surgical treatment of skin cancer or pre-cancerous lesions. So you could either have Solar Keratosis or a Basal Cell Carcinoma (BCC) or a Bowens.
Solar Keratosis is usually red and scaly and occurs most commonly on the face, the head (in balding men) and the forearms and hands. Initially they come and go but finally they are there all the time. If left untreated ± 1 % of those lesions turn into skin cancer per year - that's why we treat them!
A BCC or Bowen is already skin cancer and BCC's occur most commonly on the face and back while Bowen's is usually found on arms and legs.
Skin cancer is the most common form of cancer worldwide and in particular in our country. Almost everybody has had enough sun damage in his or her lives . to develop skin cancer when we get older.
The most common treatment for Solar Keratosis is Liquid Nitrogen (freezing them), while skin cancers are usually removed surgically. This obviously leads to scarring, which can be subtle if well done but never the less as skin cancers are almost always multiple this can be a major cosmetic problem.
That is why PDT was developed in Europe. To find a treatment which is equally effective but doesn't leave you with scars.
So how does it work?
First we apply a cream, which is called "ALA", 'also known as Levulanic acid, or Metvix (Methyl-Levulanic acid), a compound related to Bilirubin and Porphyrins (substances produced in your liver). All cells in the body need this compound, but abnormal cells absorb it faster than normal cells. The difference between the creams is that Metvix penetrates deeper, so this is what we use for the skin cancer, while we use the ALA for the pre-cancerous lesions. After we apply the cream we cover it with a Tegaderm dressing to allow it to be absorbed. After a period of 3-4 hours we take the dressing off and apply a light, which is visible red light. This light is not infrared or laser, just a very strong visible red light (635nm).
The energy from this light activates the cream and this produces Oxygen radicals. Those radicals destroy all cells that have absorbed the cream - so it destroys abnormal cells but not your normal cells.
Now while those cells get destroyed and die (which is worst during the 8-16 minutes of treatment depending on which lamp we use) it is painful- so we usually give you a Pre-medication 1 hour before the treatment. This means that someone has to drive you. If there are small spots only, we can use a local anaesthetic (then you can drive yourself home).
In the following 24 hours it will feel like a very severe sunburn: the skin will turn red, sometimes swollen, some crusting and oozing can occur if the lesions were deep.
After care treatment:
- To clean your skin use 1 heaped tablespoon salt water (dissolved in a small basin of lukewarm water) instead of using soap (twice a day).
- If there is crusting/oozing from the skin, take face cloth - DO NOT USE COTTON WOOL - and soak in salt water and leave on affected area for +- 10 mins to soak, then wipe off crusts. It does not matter if there is a bit of bleeding. Apply Bactroban afterwards (thin layer).
- It is very important to keep the area well moisturised with aqueous cream (3 to 4 times aday) - you can apply the aqueous cream over the thin layer of Bactroban.
- To relieve pain, use an ice-pack on the treated area (frozen peas work just as well and are soft).
- In those first 24 hours it may be necessary to take more Stopayne (as prescribed).
After that the area usually heals within 1-2 weeks. The skin will then peel off (like in a sunburn) and heal completely. Although it will be very unsightly for those 1-2 weeks the end results are always good.
One more word regarding the pain: the pain depends on the amount of sun damage. Sometimes it is difficult to know beforehand exactly how bad it is going to be. However it is always manageable with the Stopayne.
The reddening - which is seen after the healing - can also take up to 6 weeks sometimes, even months to disappear. Again this is an individual reaction but is never permanent.
The clearance or cure rate with this treatment is comparable to that of surgery but the cosmetic outcome is always better.
If you would like to know more, don't hesitate to ask!
The above article was compiled by Dr. Dagmar Whitaker – www.capetowndermatologists.co.za